Adjectival noun (Japanese)

An adjectival noun (Japanese: 形容動詞, "keiyō-dōshi", "adjectival verb") or sometimes just adjectival is a noun that functions as an adjective. This term is often used in analyses of the Japanese language to refer to members of the word class commonly known as "na"-adjectives".

Old Japanese

Old Japanese has one type of adjectival noun with the following inflections.

=Late Middle Japanese=

Late Middle Japanese has two types of adjectival nouns: "na" and "t-".

Modern Japanese

There is one type of adjectival noun in modern usage, with inflections as follows.

*The modern inflections are based on two primitive forms: d- and n-. The n- forms are historical older while the d- forms are newer and have replaced some of the older n- forms.
*Irrealis -daro is found with particle -u, resulting in -darou (-darō). Historically it was -dara. /au/ regularly changed into [ō] .
*Adverbial -daQ is often found with past particle -ta, resulting in "daQta" -> "datta".
*Adverbial -de is found before "aru" and "nai", as well as being used in to terminate one clause before beginning another (中止法).
*Adverbial -ni is used in adverbial constructions.
*Modern Japanese no longer inflects for imperative.

Etymology

All forms of the copula (the vehicle for the inflection of adjectival nouns) can be considered to derive from two infinitive forms, "ni" and "to". Because the copula lacked any other forms, secondary conjugations with the verb "ari" were used. The original "ni ari" and "to ari" contracted to form "nari" and "tari". To derive the modern forms "na" and "da", changes such as the following have been proposed.

For attributive "na" ("rentaikei"):
*"ni aru" > "naru" > "na"

For predicative "da" ("shūshikei"):
*"ni te ari" > "de ari" > "de a" > "da"

In some regions these changes progressed differently, resulting in forms such as "ja" or "ya".

The infinitive form "ni" is still in widespread use (e.g. "hen ni naru", "become strange"), but the form "to" has become a much rarer alternative.