Na-Adjective

Definition:

Na-adjectives (な形容詞, na-keiyōshi, called adjectival nouns or keiyōdōshi 形容動詞 in traditional Japanese grammar) are the second major adjective class in Japanese. They are so named because they require the particle な (na) when modifying a noun directly. Unlike i-adjectives which conjugate themselves, na-adjectives pattern more like nouns — they use the copula だ/です to conjugate for tense and polarity.

What Are Na-Adjectives?

Na-adjectives are a mixed class — they include:

• Many Sino-Japanese (kango) words: kirei (beautiful), shizuka (quiet), benri (convenient)
• Some loanwords (gairaigo): suteki (wonderful/stylish), hansamu (handsome)
• Some native Japanese words: hima (free-time/idle), suki (like/fond of), kirai (dislike)

They do NOT inherently end in -i (if they did end in -i, they would look like i-adjectives — but crucially, they don’t conjugate that way).

Common na-adjectives:

How to Use Na-Adjectives

Before a noun — add な (na):

As a predicate — use copula だ/です:

Conjugation of Na-Adjectives

Since na-adjectives conjugate through the copula, their paradigm follows da/desu:

Using shizuka (静か, quiet) as example:

Key takeaway: The -ni adverbial form is the na-adjective counterpart to i-adjectives’ -ku form:

• i-adj: hayai → hayaku hashiru (run fast)
• na-adj: shizuka → shizuka ni naru (become quiet)

Na-Adjectives as Nominalized Forms

Many na-adjectives can be used as nouns directly — this is because they were originally nouns:

• kirei — beauty / the state of being beautiful
• benri — convenience
• anzen — safety
• hitsuyō — necessity

This noun-like behavior is why traditional Japanese grammar categorizes them as keiyōdōshi (verbal adjectives) or adjectival nouns, separate from i-adjectives which have their own morphological paradigm.

Comparing I-Adjective and Na-Adjective Patterns

A common exercise is to see the same meaning expressed through both classes:

The i-adjective and na-adjective in each pair may have slightly different nuances or register, but this shows the parallel system.

kiraK (嫌い) and suki (好き) — “Adjective Verbs”

Suki (好き, like) and kirai (嫌い, dislike) are na-adjectives in Japanese grammar, which surprises many English learners who treat “to like” as a verb:

• Incorrect (direct English mapping): \Watashi wa neko wo suki shimasu*
• Correct: Watashi wa neko ga suki desu — As for me, cats are liked (lit.)

The particle ga marks the “object of affection” when suki/kirai are used predicatively.

Common Learner Mistakes

Using na in predicative position:

• Incorrect: \shizuka na* (as a sentence predicate)
• Correct: shizuka da / desu

Using da when attributive (before noun):

• Incorrect: \shizuka da heya*
• Correct: shizuka na heya

Forgetting ni for adverbial:

• Incorrect: \shizuka hanashite* (quietly speaking)
• Correct: shizuka ni hanashite

Decoding -i vs. na-adj:

Some na-adjectives end in -i (like kirai, kirei, hima…) and look like they might be i-adjectives — they must be memorized as na-adjectives:

• kirei (綺麗) — na-adjective
• kirai (嫌い) — na-adjective
• suki (好き) — na-adjective
• heta (下手) — na-adjective

Common Misconceptions

“Na-adjectives are just nouns pretending to be adjectives.”

While na-adjectives conjugate through the copula (だ/です) like nouns, they function syntactically as adjectives — modifying nouns directly with な (静かな部屋) and taking adverbial form with に (静かに話す). They occupy a distinct grammatical category between nouns and i-adjectives.

“Na-adjectives always need な before nouns.”

The な particle appears in attributive position (before nouns): 綺麗な花 (beautiful flower). In predicative position (end of sentence), na-adjectives take the copula directly: 花が綺麗だ. Learners sometimes add な where only the copula is needed.

“All words that take な are na-adjectives.”

Some nouns can take な in limited contexts (健康な体), and the boundary between na-adjectives and nouns is gradient. True na-adjectives can also take the adverbial に form and appear with copula conjugations across all tenses.

“Na-adjectives and i-adjectives are interchangeable if they have similar meanings.”

Even when meanings overlap (大きい/大きな), there are distributional and connotational differences. 大きな can only be attributive (before nouns), while 大きい can be both attributive and predicative. Mixing up the two classes produces grammatical errors (×静かいです, ×綺麗くない).

Practical Application

1. Learn the conjugation pattern early — Na-adjectives conjugate via the copula: 綺麗だ (plain), 綺麗です (polite), 綺麗だった (past), 綺麗じゃない (negative). This pattern is regular and covers all na-adjectives.
2. Memorize whether each new adjective is na or i — When learning a new adjective, always note its class. Dictionaries mark na-adjectives with 「な」or 「形動」(形容動詞). Getting the class wrong produces immediately noticeable errors.
3. Practice the attributive form — 静かな場所, 有名な人, 便利な道具. The な connector between adjective and noun is the defining feature.
4. Learn common na-adjectives in context — High-frequency na-adjectives include: 好き (like), 嫌い (dislike), 上手 (skillful), 下手 (unskillful), 大変 (difficult/serious), 大切 (important), 簡単 (simple), 複雑 (complex).

Sakubo supports na-adjective learning by presenting these forms in authentic Japanese sentences for spaced repetition review.

Related Terms

• I-Adjective — the other adjective class
• Verb Conjugation — parallel system for verbs
• Japanese Particles — ga/wa/ni work with adjectives
• Keigo — polite forms use de gozaimasu for formal na-adj contexts
• JLPT N5 — level where basic na-adjective use is tested

See Also

• I-Adjective — the other adjective class
• Verb Conjugation — parallel system for verbs
• Japanese Particles — ga/wa/ni work with adjectives
• Sakubo

Research

Japanese descriptive grammar (Makino & Tsutsui, 1986) provides the standard reference treatment of na-adjectives (形容動詞 keiyou-doushi) within the broader Japanese adjective system. The classification of na-adjectives as a distinct part of speech versus a subclass of nouns remains debated in Japanese linguistics — school grammar treats them as 形容動詞, while some linguists argue they are nominal adjectives.

For SLA, Iwasaki (2013) investigated L2 acquisition of the na-adjective/i-adjective distinction, finding that learners’ primary difficulty is not the conjugation patterns themselves but the classification: knowing which adjectives are na-type and which are i-type. This suggests that explicit marking of adjective class in vocabulary study (as dictionaries do) is more important than extensive conjugation drilling. Hasegawa (2015) found that conjugation errors with na-adjectives (applying i-adjective patterns) persist even at intermediate levels, recommending consistent class-marking in instructional materials.