The Verb Conjugation Map | Japanese Grammar

If you have been learning verb forms one at a time — ます here, ない there, た somewhere else — this page is where they snap together. Almost everything you can do with a Japanese verb at the beginner level is one cell of a single 4×2 table: four basic finite forms (non-past affirmative, non-past negative, past affirmative, past negative) crossed with two registers (plain and polite). "Conjugating a verb" is not recalling a random ending — it is locating the right cell.

Learn this grid until it is reflexive, and every advanced form you meet later (te-form, potential, passive, causative, conditionals, volitional) becomes just another column hanging off the same trunk.

The 4×2 core: 食べる

Here is the complete eight-cell set for the ichidan verb 食べる (to eat).

	Plain (casual)	Polite (丁寧)
Non-past affirmative	食べる	食べます
Non-past negative	食べない	食べません
Past affirmative	食べた	食べました
Past negative	食べなかった	食べませんでした

Every basic sentence you build picks exactly one of these eight. Watch the four plain cells do their work:

毎朝、卵を食べる。

maiasa, tamago o taberu

I eat eggs every morning.

朝ごはんは食べない。

asa-gohan wa tabenai

I don't eat breakfast.

ゆうべ、久しぶりに寿司を食べた。

yūbe, hisashiburi ni sushi o tabeta

Last night I had sushi for the first time in a while.

昨日は忙しくて、ほとんど何も食べなかった。

kinō wa isogashikute, hotondo nani mo tabenakatta

I was so busy yesterday I barely ate anything.

The same grid: 行く and する

The grid does not change shape for other verbs — only the endings the class demands slot into the cells. Here is the godan verb 行く and the irregular する in the very same layout.

	行く (to go)		する (to do)
	Plain	Polite	Plain	Polite
Non-past affirmative	行く	行きます	する	します
Non-past negative	行かない	行きません	しない	しません
Past affirmative	行った	行きました	した	しました
Past negative	行かなかった	行きませんでした	しなかった	しませんでした

Notice how the irregular bits are confined to single cells: 行く's euphonic past 行った sits in one plain cell, and する is memorized as し-based throughout. The grid itself is stable; only the fillers vary.

毎日、電車で会社に行きます。

mainichi, densha de kaisha ni ikimasu

I go to the office by train every day.

今日は雨だから、どこにも行かない。

kyō wa ame dakara, doko ni mo ikanai

It's raining today, so I'm not going anywhere.

先週、初めて東京に行きました。

senshū, hajimete Tōkyō ni ikimashita

I went to Tokyo for the first time last week.

結局、パーティーには行きませんでした。

kekkyoku, pātī ni wa ikimasen deshita

In the end, I didn't go to the party.

💡

Read the grid down each register column, not across. The plain column and the polite column are two parallel systems: plain builds off the dictionary form and the ない-stem; polite builds off the ます-stem. Keeping the columns separate stops you from accidentally welding a ます-piece to a plain ending.

Where every cell comes from

Each cell is derived, not memorized in isolation. Japanese attaches endings to a small set of bases, and knowing which base each ending wants is the whole game:

Dictionary form (食べる, 行く) — the plain non-past itself, and the base for many conditionals and volitional forms.
ない-stem / 未然形 (食べ-, 行か-) — the base for 〜ない, 〜なかった, the passive, and the causative.
ます-stem / 連用形 (食べ-, 行き-) — the base for 〜ます, 〜ました, 〜ません, 〜ませんでした, and 〜ましょう.
て／た-stem (食べて／た, 行って／た) — the base for the te-form, the plain past, and a huge family of te-based auxiliaries.

The map is expandable

Here is why the 4×2 core is worth over-learning: the advanced forms are just more columns bolted onto the same trunk. Once each base is solid, every new form has an obvious slot to hang on — you are not starting a new list, you are extending one map.

Form	食べる	書く	Where it lives
Plain non-past	食べる	書く	dictionary form
Polite	食べます	書きます	ます form
Negative	食べない	書かない	〜ない
Past	食べた	書いた	〜た
te-form	食べて	書いて	て-form
Potential	食べられる	書ける	potential
Passive	食べられる	書かれる	passive
Causative	食べさせる	書かせる	causative
Volitional	食べよう	書こう	volitional
Conditional (ば)	食べれば	書けば	conditionals

💡

English changes a verb in maybe five ways (walk / walks / walked / walking / to walk), so the sheer number of Japanese forms can feel overwhelming. But English forms are unrelated shapes to memorize; Japanese forms are a systematic grid built by attaching endings to four predictable bases. It is more forms but less arbitrariness — once the map is in your head, you generate forms instead of recalling them.

Common mistakes

❌ 行きなかった

ikinakatta

Incorrect: this welds the ます-stem (行き-) to the plain past-negative.

✅ 行かなかった

ikanakatta

Correct: the plain negative uses the ない-stem (行か-).

❌ 食べるます

taberu masu

Incorrect: ます doesn't attach to the dictionary form.

✅ 食べます

tabemasu

Correct: ます rides the ます-stem (食べ-).

❌ 食べませんかった

tabemasen katta

Incorrect: the polite past-negative isn't built on なかった.

✅ 食べませんでした

tabemasen deshita

Correct: ません + でした.

❌ しないでした

shinai deshita

Incorrect: mixing the plain negative with でした.

✅ しませんでした

shimasen deshita

Correct polite past-negative — or, in casual speech, しなかった.

Key takeaways

Every basic verb is one cell of a 4×2 grid: four tenses × two registers.
The grid's shape never changes — only the class-specific endings that fill it.
Read down the columns: plain and polite are parallel systems built on different bases.
Endings attach to four bases (dictionary, ない-stem, ます-stem, て／た-stem); know the base, and the ending follows.
Advanced forms are extra columns on the same trunk, not a new list.

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