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{{Short description|Category of words based on shared grammatical properties in a clause}}
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{{Distinguish|Grammatical category}}
In [[grammar]], a '''part of speech''' or '''part-of-speech''' ([[Abbreviation|abbreviated]] as '''POS''' or '''PoS''', also known as '''word class'''<ref name=rijkhoff2007>{{cite journal | last=Rijkhoff | first=Jan | title=Word Classes | journal=Language and Linguistics Compass | publisher=Wiley | volume=1 | issue=6 | year=2007 | issn=1749-818X | doi=10.1111/j.1749-818x.2007.00030.x | pages=709–726| s2cid=5404720 }}</ref> or '''grammatical category'''<ref>{{cite book |last=Payne |first=Thomas E. |title=Describing morphosyntax: a guide for field linguists |publisher=Cambridge University Press |date=1997 |location=Cambridge |isbn=9780511805066}}</ref>) is a category of words (or, more generally, of [[lexical item]]s) that have similar [[grammar|grammatical]] properties. Words that are assigned to the same part of speech generally display similar [[syntax|syntactic]] behavior (they play similar roles within the grammatical structure of sentences), sometimes similar [[morphology (linguistics)|morphological]] behavior in that they undergo [[inflection]] for similar properties and even similar [[semantic]] behavior. Commonly listed [[English language|English]] parts of speech are [[noun]], [[verb]], [[adjective]], [[adverb]], [[pronoun]], [[preposition]], [[conjunction (grammar)|conjunction]], [[interjection]], [[Numeral (linguistics)|numeral]], [[article (grammar)|article]], and [[determiner]].

Other terms than ''part of speech''—particularly in modern [[linguistics|linguistic]] classifications, which often make more precise distinctions than the traditional scheme does—include '''word class''', '''lexical class''', and '''lexical category'''. Some authors restrict the term ''lexical category'' to refer only to a particular type of [[syntactic category]]; for them the term excludes those parts of speech that are considered to be [[function word]]s, such as pronouns. The term '''form class''' is also used, although this has various conflicting definitions.<ref>John Lyons, ''Semantics'', CUP 1977, p. 424.</ref> Word classes may be classified as [[#Open and closed classes|open or closed]]: ''open classes'' (typically including nouns, verbs and adjectives) acquire new members constantly, while ''closed classes'' (such as pronouns and conjunctions) acquire new members infrequently, if at all.

Almost all languages have the word classes noun and verb, but beyond these two there are significant variations among different languages.<ref name="Krueger 2005 35">{{cite book|last=Krueger|first=Paul|title=Analyzing Grammar: An Introduction|year=2005|publisher=Cambridge University Press|location=Cambridge|isbn=978-0-521-01653-7|pages=35}}</ref> For example:
* [[Japanese language|Japanese]] has as many as [[Japanese adjectives|three classes of adjective]]s, where [[English language|English]] has one.
* [[Chinese language|Chinese]], [[Korean language|Korean]], [[Japanese language|Japanese]] and [[Vietnamese language|Vietnamese]] have a class of [[classifier (linguistics)|nominal classifier]]s.
* Many languages do not distinguish between adjectives and adverbs, or between adjectives and verbs (see [[stative verb]]).

Because of such variation in the number of categories and their identifying properties, analysis of parts of speech must be done for each individual language. Nevertheless, the labels for each category are assigned on the basis of universal criteria.<ref name="Krueger 2005 35"/>

==History==
The classification of words into lexical categories is found from the earliest moments in the [[history of linguistics]].<ref>{{cite book |author=Robins RH |year=1989 |title=General Linguistics |edition=4th |location=London |publisher=Longman}}</ref>

===India===
In the ''[[Nirukta]]'', written in the 6th or 5th century BCE, the [[Sanskrit]] grammarian [[Yāska]] defined four main categories of words:<ref name=Matilal>
{{cite book
|author = Bimal Krishna Matilal
|title = The word and the world: India's contribution to the study of language (Chapter 3)
|year = 1990
|author-link = Bimal Krishna Matilal
}}</ref>

* नाम ''nāma'' – [[noun]] (including adjective)
* आख्यात ''ākhyāta'' – [[verb]]
* उपसर्ग ''upasarga'' – pre-verb or [[prefix]]
* निपात ''nipāta'' – [[Grammatical particle|particle]], invariant word (perhaps [[preposition]])
These four were grouped into two larger classes: [[inflection|inflectable]] (nouns and verbs) and uninflectable (pre-verbs and particles).

The ancient work on the grammar of the [[Tamil language]], ''[[Tolkāppiyam]]'', argued to have been written around 2nd century CE,<ref name="Mahadevan">{{cite book |last=Mahadevan |first=I. |title=Early Tamil Epigraphy - From the Earliest Times to the Sixth century C.E., 2nd Edition |date=2014 |pages=271}}</ref> classifies Tamil words as ''peyar'' (பெயர்; noun), ''vinai'' (வினை; verb), ''idai'' (part of speech which modifies the relationships between verbs and nouns), and ''uri'' (word that further qualifies a noun or verb).<ref name=Ilakkuvan>
{{cite book
|author =Ilakkuvanar S
|title = Tholkappiyam in English with critical studies |edition=2nd
|publisher = Educational Publisher
|year = 1994
}}</ref>

===Western tradition===
A century or two after the work of Yāska, the [[Classical Greece|Greek]] scholar [[Plato]] wrote in his [[Cratylus (dialogue)|''Cratylus'' dialogue]], "sentences are, I conceive, a combination of verbs [''rhêma''] and nouns [''ónoma'']".<ref>Cratylus 431b</ref> [[Aristotle]] added another class, "conjunction" [''sýndesmos''], which included not only the words known today as [[Conjunction (grammar)|conjunctions]], but also other parts (the interpretations differ; in one interpretation it is [[pronoun]]s, [[preposition]]s, and the [[article (grammar)|article]]).<ref>''The Rhetoric, Poetic and Nicomachean Ethics of Aristotle'', translated by Thomas Taylor, London 1811, p. 179.</ref>

By the end of the 2nd century BCE, grammarians had expanded this classification scheme into eight categories, seen in the ''[[Art of Grammar]]'', attributed to [[Dionysius Thrax]]:<ref>[[Dionysius Thrax]]. τέχνη γραμματική (Art of Grammar), [http://www.hs-augsburg.de/~harsch/graeca/Chronologia/S_ante02/DionysiosThrax/dio_tech.html#11 ια´ περὶ  λέξεως (11. On the word)] {{Webarchive|url=https://web.archive.org/web/20150315015105/http://www.hs-augsburg.de/~harsch/graeca/Chronologia/S_ante02/DionysiosThrax/dio_tech.html#11 |date=2015-03-15 }}:
:λέξις ἐστὶ μέρος ἐλάχιστον τοῦ κατὰ σύνταξιν λόγου.<br />λόγος δέ ἐστι πεζῆς λέξεως σύνθεσις διάνοιαν αὐτοτελῆ δηλοῦσα.<br />τοῦ δὲ λόγου μέρη ἐστὶν ὀκτώ· ὄνομα, ῥῆμα,<br /> μετοχή, ἄρθρον, ἀντωνυμία, πρόθεσις, ἐπίρρημα, σύνδεσμος. ἡ γὰρ προσηγορία ὡς εἶδος τῶι ὀνόματι ὑποβέβληται.
:A word is the smallest part of organized speech.<br />Speech is the putting together of an ordinary word to express a complete thought.<br />The class of word consists of eight categories: noun, verb,<br />participle, article, pronoun, preposition, adverb, conjunction. A common noun in form is classified as a noun.</ref>

* 'Name' (''ónoma'') translated as 'noun': a part of speech inflected for [[grammatical case|case]], signifying a concrete or abstract entity. It includes various ''species'' like [[noun]]s, [[adjective]]s, proper nouns, appellatives, collectives, ordinals, numerals and more.<ref>The term ''[[wikt:onoma|onoma]]'' at [[Dionysius Thrax]], ''Τέχνη γραμματική'' (Art of Grammar), [https://el.wikisource.org/wiki/Τέχνη_Γραμματική#14 14. Περὶ ὀνόματος] {{Webarchive|url=https://web.archive.org/web/20220910222435/https://el.wikisource.org/wiki/%CE%A4%CE%AD%CF%87%CE%BD%CE%B7_%CE%93%CF%81%CE%B1%CE%BC%CE%BC%CE%B1%CF%84%CE%B9%CE%BA%CE%AE#14 |date=2022-09-10 }} translated by Thomas Davidson, [https://en.wikisource.org/wiki/The_grammar_of_Dionysios_Thrax#10 On the noun] {{Webarchive|url=https://web.archive.org/web/20200804023008/https://en.wikisource.org/wiki/The_grammar_of_Dionysios_Thrax#10 |date=2020-08-04 }}
: καὶ αὐτὰ εἴδη προσαγορεύεται· κύριον, προσηγορικόν, ἐπίθετον, πρός τι ἔχον, ὡς πρός τι ἔχον, ὁμώνυμον, συνώνυμον, διώνυμον, ἐπώνυμον, ἐθνικόν, ἐρωτηματικόν, ἀόριστον, ἀναφορικὸν ὃ καὶ ὁμοιωματικὸν καὶ δεικτικὸν καὶ ἀνταποδοτικὸν καλεῖται, περιληπτικόν, ἐπιμεριζόμενον, περιεκτικόν, πεποιημένον, γενικόν, ἰδικόν, τακτικόν, ἀριθμητικόν, ἀπολελυμένον, μετουσιαστικόν.
: also called ''Species'': proper, appellative, adjective, relative, quasi-relative, homonym, synonym, pheronym, dionym, eponym, national, interrogative, indefinite, anaphoric (also called assimilative, demonstrative, and retributive), collective, distributive, inclusive, onomatopoetic, general, special, ordinal, numeral, participative, independent.</ref>
* [[Verb]] (''rhêma''): a part of speech without case inflection, but inflected for [[grammatical tense|tense]], [[grammatical person|person]] and [[grammatical number|number]], signifying an activity or process performed or undergone
* [[Participle]] (''metokhḗ''): a part of speech sharing features of the verb and the noun
* [[Article (grammar)|Article]] (''árthron''): a declinable part of speech, taken to include the definite article, but also the basic [[relative pronoun]]
* [[Pronoun]] (''antōnymíā''): a part of speech substitutable for a noun and marked for a person
* [[Preposition]] (''próthesis''): a part of speech placed before other words in composition and in syntax
* [[Adverb]] (''epírrhēma''): a part of speech without inflection, in modification of or in addition to a verb, adjective, clause, sentence, or other adverb
* [[Grammatical conjunction|Conjunction]] (''sýndesmos''): a part of speech binding together the discourse and filling gaps in its interpretation

It can be seen that these parts of speech are defined by [[morphology (linguistics)|morphological]], [[Syntax|syntactic]] and [[Semantics|semantic]] criteria.

The [[Latin grammar|Latin]] grammarian [[Priscian]] ([[floruit|fl.]] 500 CE) modified the above eightfold system, excluding "article" (since the [[Latin language]], unlike Greek, does not have articles) but adding "[[interjection]]".<ref>[penelope.uchicago.edu/Thayer/E/Roman/Texts/Quintilian/Institutio_Oratoria/1B*.html This translation of Quintilian's ''Institutio Oratoria'' reads: "Our own language (Note: i.e. Latin) dispenses with the articles (Note: Latin doesn't have articles), which are therefore distributed among the other parts of speech. But interjections must be added to those already mentioned."]</ref><ref>{{cite web|url= http://www.thelatinlibrary.com/quintilian/quintilian.institutio1.shtml |via=The Latin Library |title= Quintilian: Institutio Oratoria I|access-date= 2015-09-18|archive-date= 2012-01-20|archive-url= https://web.archive.org/web/20120120203103/http://www.thelatinlibrary.com/quintilian/quintilian.institutio1.shtml|url-status= live}}</ref>

The Latin names for the parts of speech, from which the corresponding modern English terms derive, were ''nomen'', ''verbum'', ''participium'', ''pronomen'', ''praepositio'', ''adverbium'', ''conjunctio'' and ''interjectio''. The category ''nomen'' included [[substantive]]s (''nomen substantivum'', corresponding to what are today called nouns in English), [[adjective]]s ''(nomen adjectivum)'' and [[Numeral (linguistics)|numeral]]s ''(nomen numerale)''. This is reflected in the older English terminology ''noun substantive'', ''noun adjective'' and ''noun numeral''. Later<ref>See for example Beauzée, Nicolas, ''Grammaire générale, ou exposition raisonnée des éléments nécessaires du langage'' (Paris, 1767), and earlier Jakob Redinger, [https://books.google.com/books?id=C7BeAAAAcAAJ&pg=PA11 ''Comeniana Grammatica Primae Classi Franckenthalensis Latinae Scholae destinata ...''] (1659, in German and Latin).</ref> the adjective became a separate class, as often did the numerals, and the English word ''noun'' came to be applied to substantives only.

=== <span class="anchor" id="Types of Part of Speech"></span>Classification ===
Works of [[English grammar]] generally follow the pattern of the European tradition as described above, except that participles are now usually regarded as forms of verbs rather than as a separate part of speech, and numerals are often conflated with other parts of speech: nouns ([[Cardinal number (linguistics)|cardinal numeral]]s, e.g., "one", and [[collective numeral]]s, e.g., "dozen"), adjectives ([[Ordinal number (linguistics)|ordinal numeral]]s, e.g., "first", and [[Multiplier (linguistics)|multiplier numeral]]s, e.g., "single") and adverbs ([[English numerals#Multiplicative adverbs and adjectives|multiplicative numerals]], e.g., "once", and [[Distributive number|distributive numeral]]s, e.g., "singly"). Eight or nine parts of speech are commonly listed:

* [[Noun]]
* [[Verb]]
* [[Adjective]]
* [[Adverb]]
* [[Pronoun]]
* [[Preposition]]
* [[Grammatical conjunction|Conjunction]]
* [[Interjection]]
* [[Determiner]]

Some traditional classifications consider articles to be adjectives, yielding eight parts of speech rather than nine. And some modern classifications define further classes in addition to these. For discussion see the sections below.

Additionally, there are other parts of speech including [[Grammatical particle|particle]]s (''yes'', ''no''){{efn|name=yes no|1=Yes and no are sometimes classified as interjections.}} and [[postposition]]s (''ago'', ''notwithstanding'') although many fewer words are in these categories.

The classification below, or slight expansions of it, is still followed in most [[dictionaries]]:
;Noun (names): a word or lexical item denoting any abstract (abstract noun: e.g. ''home'') or concrete entity (concrete noun: e.g. ''house''); a person (''police officer'', ''Michael''), place (''coastline'', ''London''), thing (''necktie'', ''television''), idea (''happiness''), or quality (''bravery''). Nouns can also be classified as [[count noun]]s or [[mass noun|non-count nouns]]; some can belong to either category. The most common part of speech; they are called naming words.
;Pronoun (replaces or places again): a substitute for a noun or noun phrase (''them, he''). Pronouns make sentences shorter and clearer since they replace nouns.
;Adjective (describes, limits): a modifier of a noun or pronoun (''big, brave''). Adjectives make the meaning of another word (noun) more precise.
;Verb (states action or being): a word denoting an action (''walk''), occurrence (''happen''), or state of being (''be''). Without a verb, a group of words cannot be a clause or sentence.
;Adverb (describes, limits): a modifier of an adjective, verb, or another adverb (''very, quite''). Adverbs make language more precise.
;Preposition (relates): a word that relates words to each other in a phrase or sentence and aids in syntactic context (''in, of''). Prepositions show the relationship between a noun or a pronoun with another word in the sentence.
;Conjunction (connects): a syntactic connector; links words, phrases, or clauses (''and, but''). Conjunctions connect words or group of words.
;Interjection (expresses feelings and emotions): an emotional greeting or exclamation (''Huzzah, Alas''). Interjections express strong feelings and emotions.
;Article (describes, limits):a grammatical marker of definiteness (''the'') or indefiniteness (''a, an''). The article is not always listed separately as its own part of speech. It is considered by some grammarians to be a type of adjective<ref>''The Oxford Dictionary of English Grammar'' by Bas Aarts, Sylvia Chalker & Edmund Weine. OUP Oxford 2014. Page 35.</ref> or sometimes the term '[[determiner]]' (a broader class) is used.

English words are not generally [[marker (linguistics)|marked]] as belonging to one part of speech or another; this contrasts with many other European languages, which use [[inflection]] more extensively, meaning that a given word form can often be identified as belonging to a particular part of speech and having certain additional [[grammatical category|grammatical properties]]. In English, most words are uninflected, while the inflected endings that exist are mostly ambiguous: ''[[-ed]]'' may mark a verbal past tense, a participle or a fully adjectival form; ''[[-s (disambiguation)|-s]]'' may mark a plural noun, a possessive noun, or a present-tense verb form; ''[[-ing]]'' may mark a participle, [[gerund]], or pure adjective or noun. Although ''[[-ly]]'' is a frequent adverb marker, some adverbs (e.g. ''tomorrow'', ''fast'', ''very'') do not have that ending, while many adjectives do have it (e.g. ''friendly'', ''ugly'', ''lovely''), as do occasional words in other parts of speech (e.g. ''jelly'', ''fly'', ''rely'').

Many English words can belong to more than one part of speech. Words like ''neigh'', ''break'', ''outlaw'', ''laser'', ''microwave'', and ''telephone'' might all be either verbs or nouns. In certain circumstances, even words with primarily grammatical functions can be used as verbs or nouns, as in, "We must look to the ''hows'' and not just the ''whys''." The process whereby a word comes to be used as a different part of speech is called [[conversion (word formation)|conversion]] or zero derivation.

==Functional classification==
[[Linguists]] recognize that the above list of eight or nine word classes is drastically simplified.<ref>{{cite web | last=Zwicky | first=Arnold | date=30 March 2006 | title=What part of speech is "the" | work=[[Language Log]] | url=http://itre.cis.upenn.edu/~myl/languagelog/archives/002974.html | access-date=26 December 2009 | quote=...the school tradition about parts of speech is so desperately impoverished | archive-date=27 December 2009 | archive-url=https://web.archive.org/web/20091227122103/http://itre.cis.upenn.edu/~myl/languagelog/archives/002974.html | url-status=live }}</ref> For example, "adverb" is to some extent a catch-all class that includes words with many different functions. Some have even argued that the most basic of category distinctions, that of nouns and verbs, is unfounded,<ref>{{cite book |last1=Hopper |first1=P |last2=Thompson |first2=S |year=1985 |chapter=The Iconicity of the Universal Categories 'Noun' and 'Verbs' |title=Typological Studies in Language: Iconicity and Syntax |editor=John Haiman |volume=6 |pages=151–183 |location=Amsterdam |publisher=John Benjamins Publishing Company}}</ref> or not applicable to certain languages.<ref>{{cite book |last=Launey |first=Michel |year=1994 |title=Une grammaire omniprédicative: essai sur la morphosyntaxe du nahuatl classique |location=Paris |publisher=CNRS Editions}}</ref><ref>{{cite journal |last=Broschart |first=Jürgen |year=1997 |title=Why Tongan does it differently: Categorial Distinctions in a Language without Nouns and Verbs |journal=Linguistic Typology |volume=1 |issue=2 |pages=123–165 |doi=10.1515/lity.1997.1.2.123|s2cid=121039930 }}</ref> Modern linguists have proposed many different schemes whereby the words of English or other languages are placed into more specific categories and subcategories based on a more precise understanding of their grammatical functions.

Common lexical category set defined by function may include the following (not all of them will necessarily be applicable in a given language):
* Categories that will usually be [[#Open and closed classes|open classes]]:
** [[Adjective]]s
** [[Adverb]]s
** [[Noun]]s
** [[Verb]]s (except auxiliary verbs)
** [[Interjection]]s
* Categories that will usually be closed classes:
** [[Auxiliary verb]]s
** [[Coverb]]s
** [[Grammatical conjunction|Conjunction]]s
** [[determiner (class)|Determiners]] ([[article (grammar)|Articles]], [[Quantifier (linguistics)|quantifiers]], [[demonstrative]]s, and [[possessive determiners|possessives]])
** [[Measure word]]s or [[classifier (linguistics)|classifier]]s
** [[Adposition]]s (prepositions, postpositions, and circumpositions)
** [[Preverb]]s
** [[Pronoun]]s
** [[Cardinal number (linguistics)|Cardinal numerals]]
** [[grammatical particle|Particle]]s

Within a given category, subgroups of words may be identified based on more precise grammatical properties. For example, verbs may be specified according to the number and type of [[object (grammar)|object]]s or other [[complement (grammar)|complement]]s which they take. This is called [[subcategorization]].

Many modern descriptions of grammar include not only lexical categories or word classes, but also ''phrasal categories'', used to classify [[phrase]]s, in the sense of groups of words that form units having specific grammatical functions. Phrasal categories may include [[noun phrase]]s (NP), [[verb phrase]]s (VP) and so on. Lexical and phrasal categories together are called [[syntactic categories]].

[[File:EnglishGrammarCategories.png|thumb|center|600px|A diagram showing some of the posited English [[syntactic categories]]]]
{{Clear}}

==Open and closed classes==
{{See also|Function word|Content word}}

Word classes may be either open or closed. An ''open class'' is one that commonly accepts the addition of new words, while a ''closed class'' is one to which new items are very rarely added. Open classes normally contain large numbers of words, while closed classes are much smaller. Typical open classes found in English and many other languages are [[noun]]s, [[verb]]s (excluding [[auxiliary verbs]], if these are regarded as a separate class), [[adjective]]s, [[adverb]]s and [[interjection]]s. [[Ideophone]]s are often an open class, though less familiar to English speakers,<ref name="guide99">''The Art of Grammar: A Practical Guide,'' Alexandra Y. Aikhenvald, [https://books.google.com/books?id=XFBVBQAAQBAJ&pg=PA99 p. 99]</ref><ref>G. Tucker Childs, "African ideophones", in ''Sound Symbolism,''  [https://books.google.com/books?id=Uov84NavOR8C&pg=PA179 p. 179]</ref>{{efn|name=ideophones|1=Ideophones do not always form a single grammatical word class, and their classification varies between languages, sometimes being split across other word classes. Rather, they are a phonosemantic word class, based on derivation, but may be considered part of the category of "expressives",<ref name="guide99"/> which thus often form an open class due to the productivity of ideophones. Further, "[i]n the vast majority of cases, however, ideophones perform an adverbial function and are closely linked with verbs."<ref>G. Tucker Childs, "African ideophones", in ''Sound Symbolism,''  [https://books.google.com/books?id=Uov84NavOR8C&pg=PA181 p. 181]</ref>}} and are often open to [[nonce word]]s. Typical closed classes are [[preposition]]s (or postpositions), [[determiner]]s, [[grammatical conjunction|conjunction]]s, and [[pronoun]]s.<ref>{{cite web|url=http://strazny.com/encyclopedia/sample-function-words.html|title=Sample Entry: Function Words / Encyclopedia of Linguistics|access-date=2014-12-21|archive-date=2018-08-30|archive-url=https://web.archive.org/web/20180830211625/http://www.strazny.com/encyclopedia/sample-function-words.html|url-status=live}}</ref>

The open–closed distinction is related to the distinction between [[syntactic category|lexical and functional categories]], and to that between [[content word]]s and [[function word]]s, and some authors consider these identical, but the connection is not strict. Open classes are generally lexical categories in the stricter sense, containing words with greater semantic content,<ref name="Lexical and Functional categories">{{cite book|last=Carnie|first=Andrew|title=Syntax: A Generative Introduction|year=2012|publisher=Wiley-Blackwell|location=New Jersey|isbn=978-0-470-65531-3|pages=51–52}}</ref> while closed classes are normally functional categories, consisting of words that perform essentially grammatical functions. This is not universal: in many languages verbs and adjectives<ref>{{Cite journal| doi = 10.1075/sl.1.1.04dix| title = Where Have all the Adjectives Gone?| journal = Studies in Language| volume = 1| pages = 19–80| year = 1977| last = Dixon | first = Robert M. W. | author-link = Robert M. W. Dixon}}</ref><ref name="dixon2006">''Adjective classes: a cross-linguistic typology,'' [[Robert M. W. Dixon]], Alexandra Y. Aikhenvald, OUP Oxford, 2006</ref><ref name="guide97">''The Art of Grammar: A Practical Guide,'' Alexandra Y. Aikhenvald, [https://books.google.com/books?id=XFBVBQAAQBAJ&pg=PA96 p. 97]</ref> are closed classes, usually consisting of few members, and in Japanese the formation of new pronouns from existing nouns is relatively common, though to what extent these form a distinct word class is debated.

Words are added to open classes through such processes as [[Compound (linguistics)|compounding]], [[Morphological derivation|derivation]], [[Coining (linguistics)|coining]], and [[Borrowing (linguistics)|borrowing]]. When a new word is added through some such process, it can subsequently be used grammatically in sentences in the same ways as other words in its class.<ref>{{cite book|last=Hoff|first=Erika|title=Language Development|year=2014|publisher=Cengage Learning|location=Belmont, CA|isbn=978-1-133-93909-2|page=171}}</ref> A closed class may obtain new items through these same processes, but such changes are much rarer and take much more time. A closed class is normally seen as part of the core language and is not expected to change. In English, for example, new nouns, verbs, etc. are being added to the language constantly (including by the common process of [[verbing]] and other types of [[conversion (word formation)|conversion]], where an existing word comes to be used in a different part of speech). However, it is very unusual for a new pronoun, for example, to become accepted in the language, even in cases where there may be felt to be a need for one, as in the case of [[Gender-neutral pronoun#English|gender-neutral pronouns]].

The open or closed status of word classes varies between languages, even assuming that corresponding word classes exist. Most conspicuously, in many languages verbs and adjectives form closed classes of content words. An extreme example is found in [[Jingulu language|Jingulu]], which has only three verbs, while even the modern Indo-European [[Persian language|Persian]] has no more than a few hundred simple verbs, a great deal of which are archaic. (Some twenty Persian verbs are used as [[light verb]]s to form compounds; this lack of lexical verbs is shared with other Iranian languages.) Japanese is similar, having few lexical verbs.<ref>''Categorial Features: A Generative Theory of Word Class Categories,'' {{cite book| url = https://books.google.com/books?id=QoNIBQAAQBAJ&pg=PT54| title = p. 54| isbn = 9781316194638| last1 = Panagiotidis| first1 = Phoevos| date = 4 December 2014| publisher = Cambridge University Press}}</ref>{{Failed verification|date=April 2025}} [[Basque verbs]] are also a closed class, with the vast majority of verbal senses instead expressed periphrastically.

In [[Japanese language|Japanese]], verbs and adjectives are closed classes,{{sfn|Dixon|1977|p=48}} though these are quite large, with about 700 adjectives,<ref>''The Typology of Adjectival Predication,'' Harrie Wetzer, [https://books.google.com/books?id=ORUUwhdDPpUC&pg=PA311 p. 311]</ref><ref name="guide96">''The Art of Grammar: A Practical Guide,'' Alexandra Y. Aikhenvald, [https://books.google.com/books?id=XFBVBQAAQBAJ&pg=PA96 p. 96]</ref> and verbs have opened slightly in recent years. [[Japanese adjectives]] are closely related to verbs (they can predicate a sentence, for instance). New verbal meanings are nearly always expressed periphrastically by appending {{Nihongo||する|suru|to do}} to a noun, as in {{Nihongo||運動する|undō suru|to (do) exercise}}, and new adjectival meanings are nearly always expressed by [[adjectival noun (Japanese)|adjectival noun]]s, using the suffix {{Nihongo||〜な|-na}} when an adjectival noun modifies a noun phrase, as in {{Nihongo||変なおじさん|hen-na ojisan|strange {{not a typo|man}}<!-- do NOT translate this a "uncle" -->}}. The closedness of verbs has weakened in recent years, and in a few cases new verbs are created by appending {{Nihongo||〜る|-ru}} to a noun or using it to replace the end of a word. This is mostly in casual speech for borrowed words, with the most well-established example being {{Nihongo||サボる|sabo-ru|cut class; play hooky}}, from {{Nihongo||サボタージュ|sabotāju|sabotage}}.<ref>{{cite web |url=http://japaneselevelup.com/homage-to-%E3%82%8Bru-the-magical-verbifier/ |title=Homage to る(ru), The Magical Verbifier |date=2011-07-18 |author=Adam |access-date=2015-02-22 |archive-date=2021-01-15 |archive-url=https://web.archive.org/web/20210115210949/https://japaneselevelup.com/homage-to-%E3%82%8Bru-the-magical-verbifier/ |url-status=live }}</ref> This recent innovation aside, the huge contribution of [[Sino-Japanese vocabulary]] was almost entirely borrowed as nouns (often verbal nouns or adjectival nouns). Other languages where adjectives are closed class include Swahili,<ref name="guide97"/> [[Bemba language|Bemba]], and [[Luganda]].

By contrast, [[Japanese pronouns]] are an open class and nouns become used as pronouns with some frequency; a recent example is {{Nihongo||自分|jibun|self}}, now used by some as a first-person pronoun. The status of Japanese pronouns as a distinct class is disputed, however, with some considering it only a use of nouns, not a distinct class. The case is similar in languages of Southeast Asia, including Thai and Lao, in which, like Japanese, pronouns and terms of address vary significantly based on relative social standing and respect.<ref name="guide98">''The Art of Grammar: A Practical Guide,'' Alexandra Y. Aikhenvald, [https://books.google.com/books?id=XFBVBQAAQBAJ&pg=PA98 p. 98]</ref>

Some word classes are universally closed, however, including demonstratives and interrogative words.<ref name="guide98"/>

==See also==
* [[Part-of-speech tagging]]
* [[Sliding window based part-of-speech tagging]]
* [[Traditional grammar]]

==Notes==
{{Notelist}}

==References==
{{Reflist|30em}}

==External links==
{{Wiktionary category|category=Parts of speech|type=enumerating the known parts of speech in any language}}
{{Wiktionary category|category=English lemmas|type=English vocabulary organized by part of speech}}
* {{Commons category-inline|Parts of speech}}
* [https://arts.uottawa.ca/writingcentre/en/hypergrammar/the-parts-of-speech The parts of speech] {{Webarchive|url=https://web.archive.org/web/20190904171840/https://arts.uottawa.ca/writingcentre/en/hypergrammar/the-parts-of-speech |date=2019-09-04 }}
*{{cite web|url=http://grammar.ccc.commnet.edu/grammar/|title=Guide to Grammar and Writing|archive-url=https://web.archive.org/web/20181009111935/http://grammar.ccc.commnet.edu/grammar/|archive-date=9 October 2018}}
* [https://web.archive.org/web/20060912045001/http://email.eva.mpg.de/~haspelmt/2001wcl.pdf Martin Haspelmath. 2001. "Word Classes and Parts of Speech." In: Baltes, Paul B. & Smelser, Neil J. (eds.) ''International Encyclopedia of the Social and Behavioral Sciences''. Amsterdam: Pergamon, 16538–16545.] (PDF)

{{lexical categories|state=collapsed}}
{{Authority control}}

[[Category:Grammar]]
[[Category:Parts of speech| ]]