い-Adjective Conjugation in Japanese: All Tenses and Forms

い-Adjective conjugation in Japanese has eight core cells: two registers, two tenses, and two polarities. All are built by attaching suffixes to a single stem.¹² At JLPT N5, the regular paradigm is often the first Japanese word class learners meet that inflects on its own, with no copula needed to carry tense.²³

Overview

Where this article sits in the adjectives map

Modern school grammar (学校文法) recognises two productive adjective classes: 形容詞 (い-形容詞, keiyōshi) and 形容動詞 (な-形容詞, keiyōdōshi). For the two-class background and the diagnostic that tells the classes apart, see the Japanese Adjectives Overview hub.⁴⁵¹

This article covers only the regular い-形容詞 paradigm. The one common irregular item, いい / 良い, conjugates from the older stem よ- (よかった, よくない, よくて, よく) and has its own dedicated treatment in the いい / 良い irregular article.⁴⁶⁷

The regular paradigm taught here applies to the large, open set of native Yamato い-形容詞: 大きい, 寒い, 高い, 暑い, 早い, 新しい, 楽しい, 悲しい, 嬉しい, and the rest. Every form below is a "stem + suffix" derivation on those words.¹²⁸

What "conjugating" means for an い-adjective

An い-形容詞 is a predicate that fully inflects. The adjective itself carries tense and polarity, with no copula in the plain register: 大きい (non-past affirmative) → 大きかった (past affirmative) → 大きくない (non-past negative) → 大きくなかった (past negative).¹²⁹⁵

This is the structural reason 学校文法 places 形容詞 alongside verbs as a 用言 (an inflecting word class). The final い is the inflecting slot; the part before it is the stem (大き- / 高- / 寒- / 暑-). Every modern form except the bare dictionary form is built by dropping that final い and attaching a suffix.¹²⁹

今日きょうは寒さむい。²
"It's cold today."

The same six-cell school-grammar matrix used for verb conjugation (未然形・連用形・終止形・連体形・仮定形・命令形) also organises い-形容詞 conjugation. The conclusive (終止形) and attributive (連体形) forms are identical in modern Japanese, the result of a Late Middle Japanese sound change that reduced the older attributive 〜き to 〜い.¹⁰⁹⁵

高たかい本ほんを買かった。²
"I bought an expensive book."

In polite register, です attaches directly to the inflected plain form. It does not change the adjective. The です here has no syntactic function and does not predicate; it adds politeness only. The layered usage is explicitly endorsed in NHK's broadcast handbook.¹¹¹¹²

Because the adjective can predicate on its own, the plain copula だ cannot attach to an い-形容詞. *大きいだ is ungrammatical: the class already carries its own predicate marking.¹¹³⁹

The verb-like predicate

An い-形容詞 fills the predicate slot by itself. Tense, polarity, and politeness all combine on the adjective; nothing else is required to make a grammatical sentence.¹⁹⁵

The stem rule in one line

Drop the final い to get the stem. Every form below is "stem + suffix." 大きい → 大き-, 高い → 高-, 寒い → 寒-, 暑い → 暑-, 早い → 早-, 楽しい → 楽し-.¹²⁹

In school-grammar terms, the stem is the 語幹 (gokan). The inflectional suffixes that attach to it are 〜い (終止形・連体形), 〜く (連用形, the base of the adverbial and continuative), 〜かった (past), 〜くない (negative), 〜くて (te-form), and 〜ければ (conditional, not covered in this N5 article).⁹⁵¹⁰

The stem 寒- never surfaces alone in modern Japanese; it always appears with one of those inflectional suffixes. The dictionary form 寒い (stem + 〜い) is what the learner sees in vocabulary lists and what dictionaries tag as the citation form.¹⁹

The diagram shows the stem-to-suffix derivation. The eight-cell grid below fills it in cell by cell.

The Full Conjugation Paradigm

The eight core cells (plain × polite × present × past × affirmative × negative)

The regular い-形容詞 paradigm fits into an eight-cell grid. The grid crosses two registers (plain / polite), two tenses (non-past / past), and two polarities (affirmative / negative). The grid below is anchored on 大きい and is reproduced under this exact set of rows across major learner references.¹²⁸

Polarity	Tense	Plain	Polite
Affirmative	Non-past	大きい ōkii	大きいです ōkii desu
Affirmative	Past	大きかった ōkikatta	大きかったです ōkikatta desu
Negative	Non-past	大きくない ōkikunai	大きくないです ōkikunai desu / 大きくありません ōkiku arimasen
Negative	Past	大きくなかった ōkikunakatta	大きくなかったです ōkikunakatta desu / 大きくありませんでした ōkiku arimasen deshita

Tense and polarity are realised inside the adjective in every cell. The polite forms add です (or, in the older formal negative, ありません) without changing the adjective itself.¹¹¹¹²

The polite negative has two competing forms: the modern colloquial 〜くないです and the older, more formal 〜くありません. Both are correct; the choice is register, addressed in the sub-section below.¹¹¹²⁵

Present affirmative: 大きい / 大きいです

The dictionary form is the present-affirmative form. No further morphology applies in plain register. In school-grammar terms, the same surface form fills both the 終止形 (predicative slot) and the 連体形 (attributive slot before a noun).¹⁹⁵¹⁰

この鞄かばんは大おおきい。²
"This bag is big."

In polite register, です attaches with no shape change to the adjective: 大きい → 大きいです, 高い → 高いです, 寒い → 寒いです. The です is a politeness marker; semantically the adjective is already a complete predicate.¹¹¹¹²

今日きょうは暑あついです。⁸
"It's hot today."

Although it looks like "noun + copula," い-adjective + です is not a copular construction. The standard diagnostic is that です itself cannot be past-tensed here. *大きいでした is ungrammatical; the past tense must be made on the adjective (大きかったです).¹¹¹¹²

高たかい本ほんですね。⁸
"It's an expensive book, isn't it."

The attributive use has the same surface form as the predicative use: 高い本 takes the bare 高い with no な, no の, and no copula in between. One shape serves both slots.¹⁹¹⁰

Past affirmative: 大きかった / 大きかったです

The past affirmative is stem + 〜かった: 大きい → 大きかった, 高い → 高かった, 寒い → 寒かった, 暑い → 暑かった, 楽しい → 楽しかった. The polite past is the same form plus です: 大きかったです, 高かったです, 寒かったです.¹²⁸

昨日きのうは寒さむかった。²
"It was cold yesterday."

Historically, the 〜かった ending comes from the kari-katsuyō (カリ活用): a contraction of the continuative 〜く plus the existential verb あり: 寒く + あり → 寒かり → 寒かっ-. This is the source of the -k- / -kar- residue that recurs in every past, negative, and conditional cell of a modern い-形容詞.¹⁰⁹

旅行りょこうは楽たのしかったです。⁸
"The trip was fun."

The past tense belongs on the adjective, never on です. The polite past is 寒かったです, not *寒いでした. The wrong form treats the politeness marker as if it were a copula and puts past tense on it. The layered structure does not allow this.¹¹¹¹²

:::danger[Past on the adjective, not on です] *寒いでした is the most common production error of the polite past for い-形容詞. The fix is to inflect the adjective and leave です in dictionary form: 寒かったです.¹¹¹¹² :::

Present negative: 大きくない / 大きくないです / 大きくありません

The plain non-past negative is stem + 〜くない: 大きい → 大きくない, 高い → 高くない, 寒い → 寒くない, 暑い → 暑くない. The 〜く piece is the continuative form of the adjective. The 〜ない is the negative auxiliary, historically the negative of ある.¹²¹⁴⁹

この問題もんだいは難むずかしくない。²
"This problem isn't hard."

The 〜ない piece can inflect further. It is morphologically the same ない that negates verbs (行く → 行かない), which is why the past negative ends in 〜なかった rather than building on a separate past-negative suffix.¹⁴⁹¹

The polite non-past negative has two forms in modern usage. The colloquial polite is stem + 〜くないです (大きくないです, 寒くないです, 高くないです). The older formal polite is stem + 〜くありません (大きくありません, 寒くありません, 高くありません), where ありません is the polite negative of ある.^1112113

今日きょうは暑あつくないです。⁸
"It's not hot today."

今日きょうは暑あつくありません。⁸
"It is not hot today."

Both polite forms are grammatical. They differ only in register. 〜くないです is overwhelmingly the form heard in spoken Japanese and taught in modern textbooks as the default polite negative. 〜くありません is preserved in news copy, business writing, formal announcements, and older textbook materials.¹¹¹²²⁸

Past negative: 大きくなかった / 大きくなかったです / 大きくありませんでした

The plain past negative is stem + 〜くなかった: 大きい → 大きくなかった, 高い → 高くなかった, 寒い → 寒くなかった. Morphologically, 〜くなかった is the past of the 〜くない negative. The shift 〜ない → 〜なかった is the same inflection that verb-negatives undergo (行かない → 行かなかった), and the い-形容詞 past negative inherits that pattern wholesale.¹²⁸¹⁴

昨日きのうのテストは難むずかしくなかった。²
"Yesterday's test wasn't hard."

The polite past negative follows the same pattern as the polite non-past negative. The colloquial polite is stem + 〜くなかったです (大きくなかったです). The older formal polite is stem + 〜くありませんでした (大きくありませんでした), where ありませんでした is the polite past negative of ある.¹¹¹²⁸¹

旅行りょこうは楽たのしくなかったです。⁸
"The trip wasn't fun."

旅行りょこうは楽たのしくありませんでした。⁸
"The trip was not fun."

The past negative is built by inflecting the negative, not by combining a separate past-negative suffix. Once a learner sees that ない is itself a verb-like inflecting auxiliary, the cell 大きくなかった requires no new rule: it is the past of 大きくない.¹⁴⁹¹

Polite-form variants compared

The polite negative cell has two competing forms (〜くないです vs 〜くありません), and the polite past negative cell has the matching pair (〜くなかったです vs 〜くありませんでした). The meaning is identical. The choice is register.¹¹¹²¹

〜くないです and 〜くなかったです are the modern colloquial polite forms. They dominate everyday spoken polite Japanese. Mainstream learner textbooks (Genki I, Minna no Nihongo I) teach them as the default polite negative, and learners most often produce and hear them in real conversations.²⁸¹²

暑あつくないですね。⁸
"It's not hot, is it."

〜くありません and 〜くありませんでした are the older, more formal polite forms. They are preferred in news copy, formal announcements, business writing, formal speeches, and printed test materials. NHK's broadcast handbook treats both forms as acceptable in modern usage, with the ありません-based forms more typical of written and broadcast register.¹¹¹²⁵

当店とうてんの商品しょうひんは高たかくありません。¹¹
"Our store's merchandise is not expensive."

For a practical N5 rule of thumb: in conversation and informal email, use 〜くないです and 〜くなかったです. In formal writing, customer-service speech, formal emails, news reports, and test contexts where the source material uses a formal register, expect 〜くありません and 〜くありませんでした.¹¹¹²¹⁵

Pick the variant by register, not by preference

Both polite negatives are grammatical. The colloquial 〜くないです fits conversation and casual polite email; the formal 〜くありません fits broadcast, news, customer-facing announcements, and printed test materials.¹¹¹²¹⁵

Extending the Paradigm: て-Form and Adverbial Form

The て-form: stem + くて

The te-form of an い-形容詞 is stem + 〜くて: 大きい → 大きくて, 高い → 高くて, 寒い → 寒くて, 暑い → 暑くて, 楽しい → 楽しくて. Morphologically, 〜くて is the continuative form 〜く plus the linking particle て. This is the same て that builds verb te-forms.¹²⁸⁹

The main functions of 〜くて are linking two adjectives ("X and Y") and marking cause or reason ("because X, Y"). The cause reading is limited to consequences the speaker does not control, such as states, involuntary reactions, and evaluations. This parallels the te-form-of-cause restriction for verbs.¹⁸²

大おおきくて新あたらしい家いえを買かった。²
"I bought a big, new house."

寒さむくて眠ねむれなかった。⁸
"It was cold, so I couldn't sleep."

For the full usage map (the linking and causation cases in detail, the descriptive-sequence reading, and contrast with 〜が and 〜し), see the dedicated treatment of the adjective te-form.²⁸

The adverbial form: stem + く

The adverbial form of an い-形容詞 is stem + 〜く: 早い → 早く ("early, quickly"), 大きい → 大きく ("greatly, in a big way"), 高い → 高く ("highly"), 新しい → 新しく ("newly"), 楽しい → 楽しく ("enjoyably").¹²¹⁴⁹

早はやく起おきてください。⁸
"Please get up early."

The 〜く form is the renyōkei (連用形, continuative form). Morphologically, it does two things: it serves as the adverb that modifies a following verb (早く起きる "wake up early"), and it is the base from which the negative 〜くない and the te-form 〜くて are built. The く is the same morpheme in all three uses.⁹¹⁴¹⁰

A common N5 use of the 〜く form is the change-of-state construction with なる: 寒くなる ("get cold"), 大きくなる ("get bigger"), 安くなる ("become cheap"). Here, 〜く is the adverbial that modifies なる. With する instead of なる, the same construction is causative ("make it become"): 大きくする ("enlarge it"), 安くする ("make it cheap").²⁸¹

寒さむくなりました。⁸
"It has gotten cold."

安やすくしてください。⁸
"Please make it cheaper."

For the full usage map of the adverbial form (the なる / する / 言う / 走る verb compatibility cases, the listing use parallel to 〜くて in older registers, and contrast with な-adjective adverbial に), see the dedicated treatment of adverbial forms of adjectives.²¹⁴

Why these two are the same stem

The te-form 〜くて, the negative 〜くない, and the adverbial 〜く all share one underlying piece: the continuative suffix 〜く (renyōkei). Once the dictionary-form い is replaced by く, the result is the base for three forms: the adverbial by itself, the te-form by adding て, and the negative by adding ない.⁹¹⁴¹⁰

The past affirmative 〜かった is the historical exception to the い → く rule. Its k- preserves the same continuative source (it came from 〜く + あり), but the modern surface form fuses directly to 〜かった rather than going through a visible 〜く stage. This is the kari-katsuyō outcome described above.¹⁰⁹

高たかい → 高たかく / 高たかくて / 高たかくない / 高たかかった¹
"expensive → highly / expensive-and / not expensive / was expensive."

The diagram makes the い → く collapse visible. One operation feeds four cells, and the kari-katsuyō past is the one branch that fuses without showing a separate く stage.

For learners, the payoff is that once the い → く shift is recognised as the underlying operation, the whole paradigm collapses to two rules. The present-affirmative is the bare dictionary form (plain) or dictionary form + です (polite). Every other form starts from the 〜く base. The suffix that follows it determines which cell of the grid is being filled: nothing for adverbial, て for te-form, ない / なかった for negatives, and かった for past affirmative.¹⁹¹³

Nuance and Register

Plain vs. polite: register, not tense

The plain forms (大きい, 大きかった, 大きくない, 大きくなかった) are not "casual" in the sense of being careless. They are the register used in writing, in subordinate clauses, in dictionaries, and among equals in speech. The polite forms (with です or ありません) are a register layer added on top of the same paradigm.¹²⁵¹

Inside a complex sentence, the plain form is the default in non-final position regardless of how polite the final predicate is. A speaker who uses polite language at the end of a sentence still uses plain forms in relative clauses, conditional clauses, and quoted thought.¹²¹⁹

大おおきい本ほんを読よみました。²
"I read a big book."

寒さむい時ときはコートを着きる。²
"When it's cold, I wear a coat."

In dictionary citation, subtitle text, newspaper headlines, and casual conversation among peers, the plain forms are the unmarked default. The です layer appears in classroom Japanese, customer service, public speech, formal email, and any context where speaker and addressee are not equals.¹²¹¹⁵

For a fuller treatment of the plain / polite distinction across word classes, see the dedicated article on plain vs. polite Japanese (です/ます vs. だ, 丁寧体・普通体); this article states only the slice that applies to い-形容詞.¹²⁵

Why です on an い-adjective is a politeness marker, not a copula

大きいです looks like "noun + copula," but it is not. The adjective 大きい is already a complete predicate, and です is added purely for register. The construction has the form [predicate] + [politeness marker], not [noun] + [copula].¹¹¹¹²

Past-tense behaviour confirms this. If です were a real copula here, its past would surface in past-tense sentences as *大きいでした. It does not.

The past is formed on the adjective (大きかったです), and です stays in dictionary form. Here, です can only signal politeness.^1111213

大おおきいです。⁸
"It's big."

大おおきかったです。²
"It was big."

NHK's broadcast handbook explicitly endorses い-adjective + です as standard modern polite Japanese, treating the layered form (rather than the older ありません-based polite negative) as the recommended default in broadcast speech.¹¹

For the full account of the copula paradigm itself (です, だ, である) and how it differs from this layered usage, see the dedicated article on the Japanese copula. This article states only the slice that explains why です here is not a copula in the syntactic sense.¹²¹

Where each form actually shows up

The plain non-past affirmative (大きい, 寒い) appears in casual speech, in attributive position modifying nouns, in dictionary citation, and in any non-final subordinate clause regardless of how polite the final predicate is.¹²¹⁹

The plain past (大きかった, 寒かった) appears in casual narration, in subordinate clauses, and in headlines and titles where space is at a premium. The plain negative and past negative (大きくない, 大きくなかった) appear in the same casual and subordinate contexts.¹²²⁸

The colloquial polite forms (大きいです, 大きかったです, 大きくないです, 大きくなかったです) dominate everyday spoken polite Japanese: classroom Japanese, customer service in casual settings, polite conversation, and polite email.¹²¹¹²⁸

The formal polite negatives (〜くありません, 〜くありませんでした) appear in news copy, formal announcements, business writing, formal speeches, and printed test materials. In BCCWJ samples, they appear in newspaper and academic prose at much higher rates than in spoken-conversation samples.¹¹¹²¹⁶

Good to know

Attaching だ to an い-adjective (*高いだ)

The first common error is attaching the plain copula だ to an い-形容詞. The wrong shape is *高いだ. The adjective rejects だ because it already occupies the predicate slot the copula would otherwise fill.¹¹³⁹

The right shape is the bare adjective:

高たかい。¹
"It's expensive."

Past-tensing です (*寒いでした)

The second common error is past-tensing です as if it were a copula. The wrong shape is *寒いでした. です cannot carry past tense in the layered polite construction. The fix is to inflect the adjective and leave です in dictionary form.¹¹¹¹²

寒さむかったです。¹¹
"It was cold."

NHK's broadcast handbook and major learner references both flag this as the most common production error of the polite past for い-形容詞.¹¹¹¹²

Treating な-adjectives that end in い as い-adjectives

The third common error is applying い-形容詞 rules to words such as きれい, 嫌い, and 幸い. These are な-形容詞, despite the surface い ending. The wrong shape *きれくない uses the い-paradigm. The right shape uses the な-形容詞 negative built with じゃない.¹⁴⁵⁷

綺麗きれいじゃない。⁷
"It's not pretty."

For the full diagnostic that tells the two classes apart, see the Japanese Adjectives Overview hub.¹⁴⁵

Regularising the いい / 良い paradigm (*いかった)

The fourth common error is regularising いい / 良い: *いくない for "not good," *いかった for "was good." The correct inflected forms come from the older stem よ-: よくない, よかった, よくて, よく.⁴⁶¹³⁷

良よかった。¹³
"It was good."

The same stem replacement applies to compounds with いい: かっこいい inflects as かっこよかった, not *かっこいかった. For the full irregular treatment, see the dedicated いい / 良い irregular article.⁴⁶¹³⁷

Why い-adjectives behave like verbs

In 学校文法, the い-形容詞 is one of the 用言 (yōgen, inflecting word classes), alongside verbs and 形容動詞. Inflecting word classes carry tense and polarity directly on the stem. Non-inflecting classes (nouns, adverbs, prepositions, particles) cannot. The verb-like behaviour of the い-形容詞 is a class membership, not a quirk.⁵⁹¹⁷

The historical source is the kari-katsuyō (カリ活用). In Old and Middle Japanese, the continuative 〜く of an adjective could combine with the existential verb あり to form an inflecting compound (寒く + あり → 寒かり). The modern past, conditional, and negative cells of an い-形容詞 descend from that compound. Morphologically, every non-affirmative cell of a regular い-形容詞 contains a -k- or -kar- residue from this history.¹⁰⁹¹⁸

This is the structural reason an い-形容詞 does not need (and rejects) the plain copula だ. The class already has its own conjugational engine inherited from the kari-katsuyō. The copula's job of predicating a non-inflecting element is redundant.¹⁰¹⁹

For the full parts-of-speech map (the ten word classes of 学校文法 and where the inflecting classes sit inside it), see the dedicated article on parts of speech in Japanese.⁵¹⁷

Mnemonic: one stem, two suffix families

The regular paradigm reduces to two suffix families on one stem. The first family is the present-affirmative pair: 〜い for plain and 〜いです for polite. The second is the 〜く base, from which every other form is built.

From the 〜く base, the adverbial ends there (寒く), the te-form adds て (寒くて), the negatives add ない / なかった (寒くない / 寒くなかった), and the past affirmative collapses to the historical 〜かった (寒かった).¹⁹¹³

A compact one-line summary for an index card is: "い → く for everything except the dictionary form, and く + あった → かった for the past." That captures both the present operation (the い → く shift) and the kari-katsuyō residue (the -katta cell).¹⁰⁹¹³

The mnemonic accommodates the polite forms with a simple addendum: です attaches to the end of any plain form without changing it. The only exception is the polite negative, where two forms exist (〜くないです and 〜くありません) and the choice is register.¹¹¹²¹

Where this paradigm does NOT apply

The irregular いい / 良い conjugates from the older stem よ-: dictionary form いい (or 良い in formal writing), but inflected forms よかった, よくない, よくて, よく, よくなかった. The regular paradigm above describes the pattern that the いい irregular escapes from. For the full treatment, see the dedicated いい / 良い irregular article.⁴⁶¹³⁷

な-形容詞 use a completely different paradigm. The stem does not inflect. Tense and polarity are carried by the following copula: 静か → 静かだ → 静かだった → 静かじゃない → 静かじゃなかった. For the full な-形容詞 paradigm, see the dedicated な-adjective conjugation article; for the two-class diagnostic, see the Japanese Adjectives Overview hub.¹²⁸⁵

A small set of words ending in the kana い belong to the na-class despite their dictionary-form ending: きれい, 嫌い, 大嫌い, 幸い. You can identify them with the attributive test (link with な, not bare juxtaposition) and the negative test (negative built with じゃない, not 〜くない). The diagnostics belong to the adjectives overview, not to this conjugation paradigm.⁴⁶⁵⁷

The frozen attributive-only forms 大きな and 小さな coexist with the regular 大きい and 小さい. They take な before a noun (大きな夢, 小さな声) and do not appear predicatively in that shape (no *夢は大きなだ). They are not part of the regular conjugation paradigm; the standard learner reference is to treat them as lexical fossils.⁴⁶⁹

See also

• Japanese Adjectives Overview: The Two Classes (い-形容詞 vs な-形容詞)
• The Japanese Copula: です, だ, である Explained
• Polite vs. Plain Japanese: です/ます vs. だ (丁寧体・普通体)
• Parts of Speech in Japanese: The 10 Classes (品詞)
• The Nai-Form (ない形): Plain Negative of Japanese Verbs
• Pitch Accent for Japanese Verbs and Adjectives: The Binary Class Rule and Conjugation Shifts

References

Footnotes

1. Makino, Seiichi and Michio Tsutsui. A Dictionary of Basic Japanese Grammar. The Japan Times, 1986. Entries for i-adjectives (pp. 96–98, 425–428), 〜くて (pp. 247–250), です (pp. 100–102), だ (pp. 521–523), and "Characteristics of Japanese Grammar §3." ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹ ↩³⁰ ↩³¹ ↩³² ↩³³ ↩³⁴ ↩³⁵ ↩³⁶ ↩³⁷ ↩³⁸ ↩³⁹ ↩⁴⁰ ↩⁴¹ ↩⁴² ↩⁴³ ↩⁴⁴ ↩⁴⁵ ↩⁴⁶ ↩⁴⁷ ↩⁴⁸

2. Banno, Eri, Yoko Ikeda, Yutaka Ohno, Chikako Shinagawa, and Kyoko Tokashiki. Genki I: An Integrated Course in Elementary Japanese, 3rd ed. The Japan Times, 2020. Lesson 5 (i-adjective and na-adjective present-tense polite and attributive forms), Lesson 8 (short forms, past affirmative and negative for both classes), Lesson 7 (te-form of adjectives, 〜くて). Grammar index: https://wp.stolaf.edu/japanese/grammar-index/genki-i-ii-grammar-index/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹ ↩³⁰ ↩³¹

3. The Japan Foundation and Japan Educational Exchanges and Services. JLPT N5 Can-do List and Level Summary. https://www.jlpt.jp/about/levelsummary.html ↩

4. 松村明 (編). 『大辞林 第三版』. 三省堂, 2006. Entries 「形容詞」「い」「いい」「よい」「だ」「です」. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

5. 日本語教育学会 (Society for Teaching Japanese as a Foreign Language) (編). 『新版 日本語教育事典』. 大修館書店, 2005. Entries 「形容詞」「イ形容詞」「品詞」「丁寧体」. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷

6. 小学館. 『日本国語大辞典 第二版』. 小学館, 2000–2002. Entries 「形容詞」「いい」「よい」「ない」「かった」. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

7. The Electronic Dictionary Research and Development Group. JMdict / Jisho.org Part-of-Speech Tag List. Jisho.org documentation. https://jisho.org/docs ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

8. スリーエーネットワーク. 『みんなの日本語 初級I 第2版』. 3A Network, 2012. Lesson 8 (い-形容詞 present-tense polite and attributive), Lesson 12 (past affirmative and negative, polite), Lesson 16 (て-form, 〜くて, linking and reason use). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷

9. Tsujimura, Natsuko. An Introduction to Japanese Linguistics, 3rd ed. Wiley-Blackwell, 2014. Chapters on word classes, predicates, and the i-adjective inflectional paradigm. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹

10. Frellesvig, Bjarke. A History of the Japanese Language. Cambridge University Press, 2010. Sections on Old Japanese adjective classes (-ku and -shiku), the kari-katsuyō contraction (-ku + ari), and the Late Middle Japanese collapse of the conclusive / attributive distinction. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

11. NHK Broadcasting Culture Research Institute (NHK放送文化研究所). 『NHK ことばのハンドブック 第2版』. NHK出版, 2005. Broadcast-style guidance on the i-adjective + です layered polite form and on the politeness scale 〜くないです / 〜くありません. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵

12. Iori, Isao et al. (庵功雄ほか). 『初級を教える人のための日本語文法ハンドブック』. スリーエーネットワーク (3A Network), 2000. Chapters on i-adjective and na-adjective predicates, the polite-form layering of です, and the 文体 (style / register) system. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵ ↩²⁶ ↩²⁷ ↩²⁸ ↩²⁹

13. Kim, Tae. A Guide to Japanese Grammar (online edition), Adjectives chapter. https://www.guidetojapanese.org/adjectives.html (limitation: web reference; cited only for claims that align with ¹, ², and ⁹). ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

14. Martin, Samuel E. A Reference Grammar of Japanese. Yale University Press, 1975 (reprinted University of Hawaiʻi Press, 2003). Sections on adjective inflection, the adverbial / continuative 〜く, and ない as the negative of ある. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸

15. Society for the Promotion of Japanese Language Education (日本国際教育支援協会・国際交流基金). 『日本語能力試験 公式問題集 N5』. 凡人社, 2018. Sample N5 reading and grammar items treating い-adjective conjugation (present and past, affirmative and negative, polite and plain) as N5 production targets. ↩ ↩²

16. 国立国語研究所 (NINJAL). 『現代日本語書き言葉均衡コーパス』(BCCWJ). https://clrd.ninjal.ac.jp/bccwj/ ↩

17. Backhouse, A. E. The Japanese Language: An Introduction. Oxford University Press, 1993. Chapter on word classes and adjective morphology. ↩ ↩²

18. Shibatani, Masayoshi. The Languages of Japan. Cambridge University Press, 1990. Sections on adjective classes and the historical i-adjective paradigm. ↩