Can anyone provide a good formal definition of the notion of grammatical category?

I am primarily referring to morphological categories, such as case, tense, gender etc., rather than to syntactical categories (subject, direct/indirect object), or phrasal categories (NPs, VPs, etc.).

Another formulation of this question would be: what is grammatical, in a language? (as opposed to lexical, semantic, or the like). How can we define grammaticality?

Dictionaries are useless. The 10 thousand pages "Encyclopedia of Language and Linguistics" (Brown 2015) contains separate entries for such fundamental notions as "French Southern Antarctic Lands: language situation", it differentiates the entry for "Frisian lexicography" from the one for "Frisian etymology"; yet, it has no entry for "Grammatical category". Which is absurd, in my opinion.

  • These are very good and important questions. A lot depends on your theory of language. Such questions can only be answered within a particular framework. As a side note, I’d start with Plungian 2011 Введение в грамматическую семантику: Грамматические значения и грамматические системы языков мира (if you read in Russian).
    – Alex B.
    Jun 19, 2019 at 23:25
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    Subject, object, complement etc. are not categories but functions This is an important distinction.
    – BillJ
    Jun 20, 2019 at 7:53
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    @BillJ characterisations of "subject" as a "grammatical category" are easily found in literature, too. (cf. Croft's Radical Construction Grammar, p. 24). It's not my fault. Jun 20, 2019 at 8:39
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    Note that by calling subject a "function" you explain nothing, since the only certainty about functions is that they are "a relation that uniquely associates members of one set with members of another set". But set theory is not involved in the study of subjects and objects Jun 20, 2019 at 8:50
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    @AlexB. Thank you. But I obviously know Plungjan's definition. I was trying to understand how widespread this approach is, and whether there is any refurbished version of it. Apparently, there is not. Which is not a problem, I am not criticising anyone. Jun 20, 2019 at 12:32

2 Answers 2


A grammatical category of a language is a non-terminal symbol of a context free grammar of the language. A morphological category is a non-terminal which appears on the left of a phrase structure rule of the grammar which does not have any non-terminals on its right hand side.

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    This is a legit answer, thank you. But it makes the notion of grammatical category essentially useless, since it is always substitutable by the term non-terminal symbol (or pre-terminal?). Which leaves me unsatisfied. Jun 20, 2019 at 9:33
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    It is a formal answer, which means that it is essentially useless. If you want a really kinky formal definition of "grammatical category", try Montague grammar.
    – jlawler
    Jun 20, 2019 at 19:14
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    @jlawler, If the OP wanted a useful definition, he should have said so. But at least my definition makes clear that if you have no idea about the grammar of a language, then you have no idea what "grammatical category" means.
    – Greg Lee
    Jun 20, 2019 at 23:59

The various linguistic frameworks all talk about this in different ways, but I think the essence of the question comes down to the observation that in all languages there's a difference between what are commonly called "function words" and "content words" (though they may be affixes, clitics, etc instead of full words.) In any language there will be a set of things you say which have regular, non-figurative, and largely unambiguous meanings, and there will be another larger set of things you say with widespread polysemy and which are more freely used in creative extensions of meaning, and which are easily and frequently coined or borrowed from other languaged. Furthermore, the content words are often analysable as being based off of function words. For example, all verbs can be defined as subkinds of the archetypal verbs BE, DO, and HAPPEN, and all nouns are subkinds of THING. Many linguistic frameworks would analyse every lexical item as either a functional/grammatical lexeme standing by itself, or a functional/grammatical bit of meaning merged with some unique content to form a root.

All languages have grammatical/function words, and new grammatical words can develop over time from content words, a process called grammaticalisation. Wikipedia gives a good summary of four processes of grammaticalisation: semantic bleaching, phonetic erosion, morphological reduction and obligatorification.

As linguistic typology compares languages we have come to identify there are many things which humans talk about in every language. In every language you can talk about how many things there are. In every language you can talk about time. So we can talk about the semantic categories of number and temporality. Furthermore, typology has identified that many of these semantic categories are grammaticalised in lots of languages. While in theory any kind of meaning could become grammaticalised, in practice certain things are grammaticalised far more often. For example, probably every language has grammaticalised at least one of tense, aspect, mood, or evidentiality, and often more than one. So, of the 222 languages in WALS, 45% of them have grammaticalised the perfective/imperfective aspect, and 55% have not, in a very diverse distribution across the world's languages. Languages can grammaticalise very unusual things. In the Australian language Jingulu, every verb marks whether it has an associated motion of going, coming, or remaining in place. We could design conlangs which grammaticalised things which occur in no natural languages, such as whether or not an action is done with a sense of existential millenial dread or irrational baby-boomer optimism.

But despite the possibility of very rare grammaticalised concepts, there are lots of ones which typology has shown are very common. These are what the grammatical categories are, the fruit of typology. Grammatical categories are what working linguists need to know in order to study, make sense of, and document previously undocumented languages. The table below comes from Wikipedia. Linguists familiar with all these grammatical categories will likely be able to account for 90% of grammatical morphemes in any arbitrary language from anywhere in the world. Though language description is never routine, and they're sure to find something unique enough to write a PhD about.

Wikipedia's list of grammatical features.

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    But the question asks for a formal definition.
    – Greg Lee
    Jun 20, 2019 at 7:46
  • IMO this answer gives a formal enough definition: grammatical categories are the results of the linguistic typology enterprise. Covers the title, first, and third paragraphs of the question.
    – curiousdannii
    Jun 20, 2019 at 7:59
  • Thank you for explaining that categories exist. Being a linguist myself, I am more or less aware of this. What I need is a criterion for distinguishing what is grammatical from what is lexical. For example, is gender a grammatical category in English? If yes, why? If no, why? Jun 20, 2019 at 9:28
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    @Artemij Regularity and the grammaticalisation criteria of obligatoriness cover that. If you weren't after an explanation of grammatical categories you shouldn't have asked for one like you did.
    – curiousdannii
    Jun 20, 2019 at 10:12

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