Adjectival noun (Japanese)

In descriptions of the Japanese language, an adjectival noun, adjectival, or na-adjective is a noun that can function as an adjective by taking the particle 〜な -na. (In comparison, regular nouns can function adjectivally by taking the particle 〜の -no, which is analyzed as the genitive case.) Adjectival nouns constitute one of several Japanese word classes that can be considered equivalent to adjectives.

In their attributive function, Japanese adjectival nouns function similarly to English noun adjuncts, as in "chicken soup" or "winter coat" – in these cases, the nouns "chicken" and "winter" modify the nouns "soup" and "coat", respectively. Japanese adjectival nouns can also be used predicatively – in that use, they do not take the -na suffix, but normally combine with forms of the copular verb.

The terminology used to refer to these words is quite inconsistent. The Japanese name is 形容動詞 keiyō-dōshi, which literally means "adjectival verb". This is not necessarily at odds with the English term adjectival noun, since in traditional Japanese grammar, keiyō-dōshi includes the copula, while the adjectival noun in the analysis described here does not include the copula. For example, in the traditional grammar, kirei da is a keiyō-dōshi and kirei is its stem; in the analysis here, kirei is an adjectival noun and kirei da is its combination with the copula. Considering the copula is a kind of verb and kirei is a kind of noun syntactically, both terminologies make sense.

Grammatically, these words are nouns, or more technically, nominals, which function attributively (like adjectives) – the main differences being that nouns take a 〜の -no suffix when acting attributively, while these words take a 〜な -na suffix when acting attributively, and that most of these words cannot be used as the agent or patient (i.e. subject) of a sentence, but otherwise behaving essentially identically grammatically. Thus, they are variously referred to as "adjectival verbs" (literal translation), "adjectival nouns" (nouns that function adjectivally), na-adjectives (function as adjectives, take na), and na-nominals (nominals that take na). For example, Eleanor Harz Jorden refers to them as na-nominals in her textbook Japanese: The Spoken Language.

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