な-Adjective Conjugation in Japanese: All Tenses and Forms
な-adjective conjugation in Japanese is an eight-cell pattern. It combines plain and polite, present and past, and affirmative and negative forms with a fixed adjective base such as 静か. It also has three extensions for noun-modification, adverbial use, and clause-linking.12 The key point is simple: the adjective itself does not inflect. The copula does, and every cell in the paradigm is one base plus one form of the copula だ.31
Overview
Where this article sits in the adjectives map
Japanese has two productive adjective classes, traditionally labelled 形容詞 (the い-class) and 形容動詞 (the な-class).12 The Japanese Adjectives Overview hub introduces the two-class distinction and the diagnostics that sort a given word into one bucket or the other.
This article covers the full conjugation paradigm for the な-class. The parallel article for the verb-like class is い-Adjective Conjugation in Japanese: All Tenses and Forms. If you arrive here from there, expect a deliberately different shape: な-adjectives are uninflected, so the table is the copula's table, not the adjective's.
What "conjugating" means for a な-adjective
A な-adjective does not inflect on itself. The word 静か stays 静か across every cell of the paradigm, and tense and polarity live on an attached form of the copula だ.312
In modern linguistic description, な-adjectives are grouped with nouns and called "adjectival nouns" or "nominal adjectives" because they cannot host tense or negation morphology on their own.341 Eleanor Jorden's term na-nominal in Japanese: The Spoken Language encodes the same insight by treating them as a sub-type of nominal.5
The traditional school-grammar (国語文法) name 形容動詞 ("verb-like adjective") reflects an older analysis that treated this class as inflecting. Modern descriptive analyses such as Uehara (1998) and Nishiyama (1999) argue that they belong with the non-inflecting nouns.341 The two labels record the same central fact: the inflection sits on an attached copula rather than on the adjective itself. The copula paradigm itself is covered in The Japanese Copula: です, だ, である Explained.
The structural relationship is small enough to draw.
The base form in one line
The base is the bare な-adjective with the な stripped: 静か, 元気, きれい, 便利.678 Every predicate form in this article is "base + copula form." The three extensions are "base + な / に / で." Dictionaries cite the bare base as the lemma, so the entry a learner memorises is 静か, not 静かだ and not 静かな.8
あの人は元気です。7
"That person is energetic."
静かな部屋が好きです。9
"I like quiet rooms."
きれいな花ですね。9
"What pretty flowers."
Three anchor words recur in every table below: 静か (quiet), 元気 (energetic / well), and きれい (pretty / clean). Watching one base feed every cell is the fastest way to internalise the paradigm.
The Full Conjugation Paradigm
The eight core cells (plain × polite × present × past × affirmative × negative)
This is the table the article exists for. The anchor word is 静か (shizuka, "quiet"). The header captures the operating insight: every cell in the grid is the copula paradigm; only the base in front of it is the adjective.
| Plain (普通体) | Polite (丁寧体) | |
|---|---|---|
| Present (+) | 静かだ | 静かです |
| Past (+) | 静かだった | 静かでした |
| Present (−) | 静かじゃない / 静かではない | 静かじゃありません / 静かではありません |
| Past (−) | 静かじゃなかった / 静かではなかった | 静かじゃありませんでした / 静かではありませんでした |
The same eight-cell shape applies when the slot in front of the copula is a noun (学生だ / 学生でした / 学生じゃない …). This is the structural reason な-adjectives are classed with nouns.26108 The adjective stem 静か carries no tense or polarity morphology in any cell; all eight contrasts are realised on the copula.312
Present affirmative: 静かだ / 静かです
The plain present requires だ. Bare 静か is not a complete predicate at the end of a sentence in neutral plain speech. This contrasts with an い-adjective, which is complete on its own.678 The polite present is です; in this paradigm です is the polite alternant of だ, not a stack on top of it.278
Dictionaries cite the lemma without だ. The lookup entry is 静か, not 静かだ.8
図書館は静かです。7
"The library is quiet."
この機械は便利だ。8
"This machine is convenient."
子どもが元気です。7
"The child is energetic."
Past affirmative: 静かだった / 静かでした
The plain past is だった, the past form of だ. The polite past is でした, the past form of です.278 The base 静か itself does not change shape; only the copula carries tense.312
昨日の試験は簡単でした。7
"Yesterday's exam was easy."
昔はあの町が静かだった。8
"That town used to be quiet."
先週は暇でした。7
"I was free last week."
Present negative: 静かじゃない / 静かではない / 静かじゃありません / 静かではありません
The present negative has four surface forms. They are not four separate rules. They are the cross-product of two independent axes: register (では formal, じゃ colloquial) and politeness (ない plain, ありません polite).121078
| Register / Politeness | Plain (ない) | Polite (ありません) |
|---|---|---|
Formal (では) | 静かではない | 静かではありません |
Colloquial (じゃ) | 静かじゃない | 静かじゃありません |
じゃ is the phonological contraction of では, with a documented path [dewa] > [dea] > [dya] > [dža].11 All four forms have the same grammatical meaning. The difference is sociolinguistic, not semantic.2811
この部屋は静かじゃない。10
"This room isn't quiet."
駅の周りは安全ではありません。7
"The area around the station is not safe."
田中さんは元気じゃありません。7
"Mr Tanaka isn't well."
Past negative: 静かじゃなかった / 静かではなかった / 静かじゃありませんでした / 静かではありませんでした
The past-negative cell is the present negative with one swap. Replace the final ない with its past form なかった, or add でした to ありません.278 The same では / じゃ register split applies, and so does the same ない / ありません politeness split.28
| Register / Politeness | Plain | Polite |
|---|---|---|
Formal (では) | 静かではなかった | 静かではありませんでした |
Colloquial (じゃ) | 静かじゃなかった | 静かじゃありませんでした |
試験はそんなに簡単じゃなかった。7
"The exam wasn't all that easy."
昨日は暇ではありませんでした。7
"I wasn't free yesterday."
あの学生は真面目じゃありませんでした。8
"That student wasn't diligent."
Polite-form variants compared
じゃない and じゃありません are the modern colloquial polite forms. Current beginner textbooks such as Genki and Minna no Nihongo teach these for conversation.712 ではない and ではありません are older and more formal. They predominate in news writing, business writing, formal speech, and JLPT reading materials.811
In practice, beginner Japanese teaches じゃありません first as the productive polite negative, and ではありません enters later as the written and business register equivalent.712
じゃ readings sound conversational. A business email or news article that uses 静かじゃありません instead of 静かではありません reads as off-register. It is like an English memo that writes "isn't" instead of "is not," which can read as too casual. The mapping is reliable: では for writing and formal speech, じゃ for conversation.811
Extending the Paradigm: な, に, and で
The attributive form: base + な (静かな + noun)
When a な-adjective modifies a noun directly, attach な between the base and the noun: 静かな部屋, 元気な子, 便利な道具.12678 This is the form that gives the class its modern name "な-adjective" / "ナ形容詞".1
The な is historically the attributive form of the classical copula なり / なる; the documented chain is に ある > なる > な.312 That is why な appears only here: between the base and a noun. It never appears in the predicate slot at the end of a sentence. The attributive vs. predicative split that this な turns on is treated in its own article. The の Particle: Possessive, Nominalizer, Attributive covers the related の / な diagnostic for dual-class words.
静かな部屋を探しています。9
"I'm looking for a quiet room."
元気な犬ですね。7
"What an energetic dog."
便利な道具を買いました。12
"I bought a convenient tool."
The adverbial form: base + に (静かに)
Attach に to the base to form the adverb that modifies a verb: 静か → 静かに ("quietly"), 元気 → 元気に ("energetically"), きれい → きれいに ("cleanly, neatly").1268 The に here is the adverbial (continuative) form of the same copula whose attributive is な; both come out of the classical なり-paradigm.31
This mirrors the い-adjective's く-adverbial form. If you already know 大きく ("greatly") and 静かに ("quietly"), you have both halves of the picture: one class uses く, the other uses に, and both turn an adjective into a verb-modifier.28 The adverbial forms of both classes are covered together in their own article.
静かに歩いてください。7
"Please walk quietly."
元気に暮らしています。12
"I'm living in good health."
部屋をきれいにしてください。7
"Please make the room clean."
The te-form: base + で (静かで)
The te-form of a な-adjective is "base + で": 静か → 静かで, 元気 → 元気で, 便利 → 便利で.1268 The で here is the te-form of the copula だ; the historical chain is に て ある > で ある > で あ > だ.31 The te-form links two adjectives or clauses. It can also supply a "because-X" cause reading. The construction parallels the い-adjective's くて but uses a different morpheme; the adjective te-form article treats both halves and the listing-vs-causal split.28
The copula te-form で is morphologically distinct from the particle で (means, location). They look identical on the surface, but they sit in different syntactic slots. The copula で follows an adjective or noun and links the clause. The particle で attaches to a noun phrase and marks means or location.8 The で Particle: Means and Location of Action covers the particle in its own right.
あの道具は便利で安い。8
"That tool is convenient and cheap."
子どもが元気で安心しました。12
"I was relieved that the child was well."
Why な, に, and で are the same paradigm
The three extensions are not three independent rules. They are three forms of the same copula attaching to the same base.312 な is the attributive form of the copula. に is the adverbial (continuative) form. で is the te-form. The predicate forms (だ, です, でした, じゃない, ではない) and the three extensions (な, に, で) all belong to one inflectional paradigm. That paradigm is applied to a na-adjective base.31610
Once you see this, the eight predicate cells and the three extensions collapse to a single rule: keep the base, then pick the form of the copula that fits the slot.6108
Nuance and Register
Plain vs. polite: register, not tense
The plain forms (静かだ, 静かだった, 静かじゃない, 静かじゃなかった) and the polite forms (静かです, 静かでした, 静かじゃありません, 静かじゃありませんでした) express the same facts. The contrast is register, not tense or polarity.28
Plain forms appear among intimates, in writing, in subordinate clauses, and in dictionaries. Polite forms appear in classroom Japanese, customer-facing speech, and formal email.7812 Polite vs. Plain Japanese: です/ます vs. だ (丁寧体・普通体) covers the wider register system that hosts both sets.
では vs. じゃ: formality, not grammar
では and じゃ are grammatically equivalent. じゃ is the phonological contraction of では, and the choice between them is stylistic: formal versus colloquial.211 The documented contraction path is [dewa] > [dea] > [dya] > [dža]; this is a regular Japanese phonetic-fusion process, not an irregular alternation.11
The では sequence itself is で (te-form of the copula) plus は (topic particle). That decomposition is why the contraction stops at じゃ and does not extend further: the contraction acts on the で + は cluster as a unit.211
Where each form actually shows up
In casual speech, the plain present だ is often dropped at the end of a sentence, leaving the bare base: 静か。 instead of 静かだ。 This drop is especially common in questions (静か？) and in women's-speech registers.210
Ending a sentence with overt だ after a な-adjective reads as more assertive and is associated with masculine-leaning speech in some registers; the same effect is reported for the noun copula だ.210
ではありません is the form expected in news writing, business writing, formal speech, and JLPT reading passages. じゃありません is the form expected in spoken textbook Japanese and casual polite conversation.7812
Dual-class words (元気, 健康, 自由, 普通)
Some words are both a noun and a な-adjective: 元気, 健康, 自由, 普通 all admit both readings.18 The na-adjective vs. noun boundary is where this dual classification is worked out in full. The diagnostic is which particle attaches before a following noun: な indicates the な-adjective use, の indicates the noun use.18
元気な子7
"an energetic child" (adjective use)
元気の秘訣8
"the secret of vitality" (noun use)
The modern linguistic analysis that na-adjectives are a sub-type of noun (Uehara 1998, Nishiyama 1999) makes this dual classification expected. Every な-adjective is already a kind of noun, so a word doing both jobs is the unmarked case rather than the exception.34 The dedicated article on the noun / な-adjective boundary covers the diagnostic in detail; for now, the な-vs-の test is the working rule.
Good to know
Adding い-adjective morphology to a な-adjective
A frequent beginner error is treating 静か as if it were an い-adjective and ending the sentence with 静かいです. That form does not exist. な-adjectives do not take い in any cell, and stacking い + です is the い-adjective paradigm leaking into the wrong class. The base 静か is final; only the copula attaches.67 The correct polite present is:
静かです。7
"It's quiet."
Stacking だ and です
Another common error is writing 静かだです, as if だ and です could co-occur. They cannot. だ and です are two forms of the same copula at different register levels, so they do not stack. The polite alternant of 静かだ is just 静かです.78 The correct forms are:
静かだ。8
"It's quiet." (plain)
静かです。7
"It's quiet." (polite)
Dropping the attributive な before a noun
A third error is writing 静か部屋, omitting な before the noun. Before a noun, the attributive copula slot is mandatory for な-adjectives. That slot is filled by な, historically the attributive form of the classical copula なり.31 The correct attributive form is:
静かな部屋9
"a quiet room"
Treating きれい, 嫌い, 有名 as い-adjectives
A fourth error is conjugating きれい, 嫌い, or 有名 as if they were い-adjectives, producing forms such as きれかったです. These words end in the /-i/ sound in their hiragana spelling, but they are な-adjectives whose dictionary form happens to end that way. The kanji spellings (綺麗, 嫌い, 有名) make the analysis visible. In 綺麗, the い is enclosed inside the kanji, so it is not okurigana. In 嫌い and 有名, the い is fixed in the dictionary form rather than the inflecting tail of an い-adjective stem.1613 The correct past polite for きれい is:
きれいでした。1
"It was pretty."
The Japanese Adjectives Overview hub carries the full diagnostic for sorting a word into the two classes.
Sentence-final bare だ after a な-adjective
The bare-だ ending (静かだ。) carries a more assertive, masculine-leaning tone in some spoken registers. Conversational style across genders often drops だ to leave 静か。 It may also pair だ with a sentence-final particle such as 静かだよ or 静かだね.210 Sentence-final particles are the standard way to soften the bare-だ ending without losing the copula's grammatical function.
じゃ in formal writing
じゃない and じゃありません are conversational. The written and formal-speech equivalents are ではない and ではありません. Using じゃ in business email or news copy reads as too casual.811 In a JLPT reading passage or a 新聞 article the negative will almost always be では-based, not じゃ-based.
The な of a な-adjective is the classical copula なり
Modern な derives from the chain に ある > なる > な, which is the attributive form of the classical copula なり (itself from ni ari). Modern だ derives from the parallel chain に て ある > で ある > で あ > だ.31 The rule "a な-adjective conjugates by attaching the copula" is therefore not coincidence. な, に, で, だ, and です are all reflexes of one classical copula paradigm, surfacing in different syntactic slots.312
One base, one copula
The whole paradigm reduces to a single instruction: keep the base (静か) untouched, and conjugate the copula in whichever slot is needed. Use だ or です for predicate present, だった or でした for past, じゃない or ではない for negative, な for attributive, に for adverbial, and で for te-form. A learner who already controls the copula paradigm already controls な-adjective conjugation.6108 The full copula reference is The Japanese Copula: です, だ, である Explained.
Why 形容動詞 is itself a memory hook
The school-grammar name 形容動詞 ("verb-like adjective") records the historical analysis that this class inflects. The modern descriptive labels nominal adjective, adjectival noun, and na-nominal record the modern analysis that it does not. Holding both labels in mind helps you remember the central fact about the class: the inflection sits on an attached copula, not on the adjective itself.3415 Parts of Speech in Japanese: The 10 Classes (品詞) covers the wider inflecting-vs-nominal map this fact sits inside.
Why this paradigm differs from い-adjectives
い-adjectives inflect on themselves: 大きい → 大きかった → 大きくない. They need no copula to carry tense or polarity, because the い-adjective is itself a complete predicate.28 な-adjectives do not inflect. The base stays fixed, and the copula carries everything. That asymmetry is why 静かだった is correct and 静かかった is meaningless, and why 大きいだ is wrong but 静かだ is right. The contrast is covered in detail in い-Adjective Conjugation in Japanese: All Tenses and Forms.
See also
- The いい / 良い Irregular: Why the Past Is よかった
- Pitch Accent for Japanese Verbs and Adjectives: The Binary Class Rule and Conjugation Shifts
- Okurigana: When Kanji Bleeds Into Hiragana
- The に Particle: A Multi-Function Workhorse
- How Japanese Grammar Works: A Big-Picture Overview