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Base — Conjugation master reference

BASE · 基礎 みんなの日本語 · Mini no Nihongo

Base · verb & adjective conversion

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REFConjugation master reference

You anchor on ます. Drop ます to get the stem, then apply the group's rule. The group must be learned with each verb — the stem alone doesn't always reveal it.

Identifying the group

GroupStem ends inExamples
1 (godan / 五段ごだん)i-sound
2 (ichidan / 一段いちだん)e-sound, or i-sound
3 (irregular)—

The ambiguity: both 帰かえります (G1) and 起おきます (G2) have i-sound stems. Verbs like 帰かえる ·入はいる· 走はしる · 切きる · 知しる · 要いる · 減へる look ichidan but are godan. Learn the group with the word.

Group I — godan (五段動詞ごだんどうし)

ますdictないてたpotentialvolitional

う-verbs take わない, not あない: 買かう→買かわない.

Exception:行いきます→行いく→行いって/行いった(not 行いいて).

Group II — ichidan (一段動詞いちだんどうし)

ますdictないてたpotentialvolitional

Group III — irregular

ますdictないてたpotentialvolitional

来くるreadings shift: きます / くる / こない / きて / きた / こられる / こよう

て-form sound changes (音便おんびん) — the master table

EndingChangeてたExample
no contraction

All verb forms at a glance

FormMade fromLesson
baseL4
onbin table aboveL14
a-row + ないL17
i-row → u-rowL18
て形けい, て→たL19
full plain paradigmL20
u-row → e-row + るL27
u-row → o-row + うL31
u→e / dict + なL33
u-row → e-row + ばL35
a-row + れるL37
a-row + せるL48

Look-alikes to keep apart:

書かける potential · 書かかれる passive · 書かかせる causative

For Group II, potential and passive are identical(食たべられる) — only context tells them apart.

Plain past-negative — universal rule

Take the ない-form, drop い, add かった: 書かかない → 書かかなかった. Works for every group and for adjectives.

い-adjectives (い形容詞けいようし)

FormPolitePlain
present +
present −
past +
past −
te-form (linking)
adverb
+ noun
conditional

いい is irregular throughout: よくない · よかった · よくなかった · よくて · よく · よければ · よさそう

な-adjectives (な形容詞けいようし)

FormPolitePlain
present +
present −
past +
past −
te-form (linking)
adverb
+ noun
conditional

な-adj differs from い-adj in four places: で (not くて) to link · に (not く) for adverb · な before a noun · なら (not ければ) for conditional.

な-adjectives whose reading ends in い:きれい ·嫌きらい·大嫌だいきらい·有名ゆうめい — they still take な before a noun and なら in the conditional.

What follows what — the だ question

Patternな-adj / noun takesLesson
L21
L47
L28
drop だ (便利べんりでしょう)L21/32
drop だL32
drop だL40
L26
L39
L45
L47
L23/45
L46

This table alone accounts for a large share of mistakes from L21 onward.

詳説 In depth — grammar notes

Four words, four forms — the whole system on one screen

Japanese has exactly four word classes that change shape: verbs, い-adjectives, な-adjectives and nouns. Each one has the same four slots. Learn the grid, not a list of endings.

presentpastnegativepast negative
verb
い-adj
な-adj
noun

な-adjectives and nouns behave identically. Everywhere in this table, and in almost every pattern in the two books, whatever you do to you do to . That halves what you have to remember.

The one that breaks the pattern is the い-adjective: its past and negative live inside the word (高たかかった), and です is only added afterwards for politeness. ✕ — です itself never carries the tense of an い-adjective.

The same grid, plain form

Plain forms are what you need before という, と思おもう, んです, から, ので, のに, 場合ばあい, ばかり, はず, そう, ようだ — that is, before most of Book II.

presentpastnegativepast negative
verb
い-adj
な-adj
noun

Written and formal Japanese prefers over : · . じゃ is the spoken contraction of では — same meaning, lighter register.

Politeness: two axes, not one

PolitenessFormality of the negativeExample
polite, standard
polite, softer
polite, formal
plain

Verbs — find the group, then everything follows

Every verb form in the language is built from one of four stems. Get the group right and there is nothing left to guess — so settle this question first. It does have an answer.

Deciding the group from the ます-form

For most of Book I a verb reaches you as , so start from what you actually have in front of you: the kana immediately before ます.

StepAskThen
1Is it or ?III — there are only these two.
2Is the kana before ます an e-sound? (え·け·せ·て·ね·へ·め·れ·げ·ぜ·で·べ·ぺ)II, with no exceptions — a Group I stem is never on the え-row.
3It is an i-sound. Is the verb one of the short list below?II.
4OtherwiseI — the default, and where most verbs land.
Group II because the stem is e-row
Group II although the stem is i-row
Group I — every other i-row stem

Only the middle row has to be memorised. An e-row stem decides itself; the い-row is Group I by default, but the middle row is a list you keep adding to rather than one you finish — nothing in the kana distinguishes 起おきます from 書かきます. Learn each new verb with its group. See L14.

The same decision from the dictionary form

Once you have the dictionary form (L18) the test is one glance instead of four steps.

GroupHow to spot itExamples
II (一段いちだん)ends in -eru or -iru
IIIonly two verbs
I (五段ごだん)everything else

Verbs that look like Group II but are Group I: · · · · · · . Those seven are the ones you meet first — they are not the whole list ( behave the same way), so the habit to build is to learn the group with the word, the way you learn its kanji.

The four stems

StemGroup I: 書かくGroup II: 食たべるBuilt from it
ない-stem (あ-row)negative, passive, causative
ます-stem (い-row)ます, たい, ながら, やすい, すぎる, なさい
dictionary (う-row)plain present, こと, ために, つもり, な (prohibitive)
ば/え-stem (え-row)— (Group I only)conditional ば, potential, imperative

Group II has no え-stem. Its conditional, potential and imperative are built by dropping る and adding れば / られる / ろ: . Reading as a stem and adding る is exactly where comes from — see the register note in L27.

SlotGroup I recipeGroup II recipeする来くる
polite
plain presentdictionarydictionary
plain negative
plain pastて-form, て→た
plain past neg.negative, い→かったsame
て-formsound change (below)
potential
volitional
conditional
passive
causative
imperative

Verbs ending in う take わ, not あ, in the あ-row: . Never .

て-form sound changes (Group I only)

Dictionary ends inChangeExample
irregular

The past plain form is the て-form with て→た, で→だ. If you know you already know . Nothing new to learn.

い-adjectives — the tense lives in the word

FormRecipe高たかいいい (irregular)
presentas-is
past
negative
past negative
adverb
て-form
becomes
before a nounas-is

conjugates from its older form in every slot except the plain present. ✕ · ○. This also hits every compound: , .

is itself an い-adjective, which is why every negative in the language ends the same way: , , . One rule covers every past negative in Japanese: い → かった.

な-adjectives and nouns — identical machinery

FormRecipe元気げんき (な-adj)学生がくせい (noun)
polite present
polite past
polite negative
polite past neg.
plain present
て-form
adverb—
becomes
before a noun

The only difference between the two classes is that last row: な-adjectives take な before a noun, nouns take の. Everywhere else they are the same word class as far as the grammar is concerned.

What happens to だ in front of other grammar

This is where most Book II mistakes come from. Same word, four different shapes depending on what follows.

Followsな-adj / noun becomesExample
bare
noun
bare

Transformations, one step at a time

Never jump straight to the answer. Each of these is a chain of small moves.

TargetRouteWorked example
polite past negativeます → ません → ませんでした
plain past negativedictionary → ない → なかった
い-adj past negative
な-adj past negative
potential past
passive negative
causative て-form

Potential, passive and causative all produce Group II verbs. Once you reach , or , every further change is the easy Group II pattern: drop る and add ます / ない / た / て.

The traps that cost the most marks

No one has measured these, and this is not a frequency table — it is a teacher's list of the slips that keep coming back in written work, in the order they are worth fixing.

✕○Why
い-adjectives carry their own past
い-adjectives negate with くない
な-adjectives negate with じゃない
いい conjugates as よい
う-verbs take わ in the あ-row
な / の before ので, のに, はず
だ before から, し, と思おもう

(ら抜ぬき言葉ことば) does not belong in that table. It is a register, not a slip: most speakers under fifty say it, and you will hear it constantly. Textbooks, exams and anything written still want — L27 sets the two side by side.

The trap this page cannot conjugate away

Every row above is morphology — endings, stems, vowel rows — because that is what a conjugation reference can drill. The mistake that outlasts all of them is は vs が, and it is not a conjugation at all: both particles are correct forms, so nothing marks the wrong one wrong except the meaning.

MarkerWhat it saysExample
you already know the subject; the predicate is the new part
the subject is the new part — an answer, or news
this one, as against the others

A question word never takes は: ✕ · ○ — and the answer keeps が, because it is the part being supplied. Contrastive は is worked out properly in L27.

Test yourself in two minutes

The fastest check is to take one word and say all four forms out loud, twice: polite, then plain. If any slot makes you pause, that is the slot to drill.

Say these four, then the plain versions
verb
い-adjective
な-adjective
noun

Cover the right column

PromptAnswer

Then open the conjugation trainer — it generates these endlessly, checks what you type in kana, and keeps score by form so you can see which slot is actually weak. It is linked from the top of this page and from the home screen.

Try translating

EnglishJapanese
I didn't drink coffee yesterday.
It wasn't expensive. (plain)
This room isn't quiet.
I was a student last year. (plain)
The weather wasn't good yesterday.
Who came? — Mr Miller came.

練習 Practice — 30 questions

  1. Q1 Group I · godan

    ます → dictionary form

    書 か
    き
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B godan: stem i-sound → u-sound. 書かき→書かく
  2. Q2 Group I · godan

    ます → dictionary form

    飲 の
    み
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A み→む (m-column i→u)
  3. Q3 Group I · godan

    ます → dictionary form

    買 か
    い
    ま
    す
    1. A
    2. B
    3. C
    4. D
    C い→う
  4. Q4 Group II · ichidan

    ます → dictionary form

    食 た
    べ
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A ichidan: stem + る
  5. Q5 Group II · ichidan

    ます → dictionary form

    起 お
    き
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B ichidan: 起おき + る
  6. Q6 Group III · irregular

    ます → dictionary form

    来 き
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A 来きます→来くる(くる)
  7. Q7 Group I · godan

    ます → ない form

    書 か
    き
    ま
    す
    1. A
    2. B
    3. C
    4. D
    C godan: stem i→a + ない. 書かき→書かか+ない
  8. Q8 Group I · う-ending

    ます → ない form

    買 か
    い
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B う-verbs → わない (not あない)
  9. Q9 Group I · godan

    ます → ない form

    飲 の
    み
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A み→ま+ない
  10. Q10 Group II · ichidan

    ます → ない form

    食 た
    べ
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B ichidan: stem + ない
  11. Q11 Group III · irregular

    ます → ない form

    し
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B する → しない
  12. Q12 Group I · く

    ます → て form

    書 か
    き
    ま
    す
    1. A
    2. B
    3. C
    4. D
    C く → いて
  13. Q13 Group I · む

    ます → て form

    飲 の
    み
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A む/ぶ/ぬ → んで
  14. Q14 Group I · つ

    ます → て form

    待 ま
    ち
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B う/つ/る → って
  15. Q15 Group II · ichidan

    ます → て form

    食 た
    べ
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A ichidan: stem + て
  16. Q16 Group I · ぐ

    ます → た form

    泳 およ
    ぎ
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B ぐ → いだ (voiced)
  17. Q17 Group I · す

    ます → た form

    話 はな
    し
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A す → した
  18. Q18 Group I · exception

    ます → た form

    行 い
    き
    ま
    す
    1. A
    2. B
    3. C
    4. D
    B 行いくis the exception →行いった
  19. Q19 → なかった

    ます → past negative plain

    飲 の
    み
    ま
    す
    1. A
    2. B
    3. C
    4. D
    A 飲のまない → drop い + かった
  20. Q20 い形容詞

    い-adj → present negative plain

    高 たか
    い
    1. A
    2. B
    3. C
    4. D
    B drop い → く + ない
  21. Q21 い形容詞

    い-adj → past affirmative plain

    寒 さむ
    い
    1. A
    2. B
    3. C
    4. D
    B い → かった
  22. Q22 い形容詞 · て

    い-adj → te-form (linking)

    安 やす
    い
    1. A
    2. B
    3. C
    4. D
    B い → くて
  23. Q23 い形容詞 · adverb

    い-adj → adverb (becomes ~)

    大 おお
    き
    い
    1. A
    2. B
    3. C
    4. D
    A い → く (→大おおきくなります)
  24. Q24 い形容詞 · irregular

    い-adj IRREGULAR → past +

    い
    い
    1. A
    2. B
    3. C
    4. D
    C いい → よかった
  25. Q25 な形容詞

    な-adj → present affirmative plain

    元気 げんき
    1. A
    2. B
    3. C
    4. D
    B plain present + = だ
  26. Q26 な形容詞

    な-adj → present negative plain

    便利 べんり
    1. A
    2. B
    3. C
    4. D
    B じゃない (like a noun)
  27. Q27 な形容詞

    な-adj → past affirmative plain

    静 しず
    か
    1. A
    2. B
    3. C
    4. D
    B だった
  28. Q28 な形容詞 · て

    な-adj → te-form (linking)

    き
    れ
    い
    1. A
    2. B
    3. C
    4. D
    B な-adj links with で (not くて)
  29. Q29 な形容詞 · adverb

    な-adj → adverb (becomes ~)

    元気 げんき
    1. A
    2. B
    3. C
    4. D
    B に (→元気げんきになります)
  30. Q30 な形容詞 · + noun

    な-adj → modifying a noun: ___ 人ひと

    親切 しんせつ
    1. A
    2. B
    3. C
    4. D
    B な before the noun:親切しんせつな人ひと

解答 Answer key

  1. Q1 B godan: stem i-sound → u-sound. 書かき→書かく
  2. Q2 A み→む (m-column i→u)
  3. Q3 C い→う
  4. Q4 A ichidan: stem + る
  5. Q5 B ichidan: 起おき + る
  6. Q6 A 来きます→来くる(くる)
  7. Q7 C godan: stem i→a + ない. 書かき→書かか+ない
  8. Q8 B う-verbs → わない (not あない)
  9. Q9 A み→ま+ない
  10. Q10 B ichidan: stem + ない
  11. Q11 B する → しない
  12. Q12 C く → いて
  13. Q13 A む/ぶ/ぬ → んで
  14. Q14 B う/つ/る → って
  15. Q15 A ichidan: stem + て
  16. Q16 B ぐ → いだ (voiced)
  17. Q17 A す → した
  18. Q18 B 行いくis the exception →行いった
  19. Q19 A 飲のまない → drop い + かった
  20. Q20 B drop い → く + ない
  21. Q21 B い → かった
  22. Q22 B い → くて
  23. Q23 A い → く (→大おおきくなります)
  24. Q24 C いい → よかった
  25. Q25 B plain present + = だ
  26. Q26 B じゃない (like a noun)
  27. Q27 B だった
  28. Q28 B な-adj links with で (not くて)
  29. Q29 B に (→元気げんきになります)
  30. Q30 B な before the noun:親切しんせつな人ひと