水平 (suihei) conjugation
level, horizontal
水平 (すいへい, suihei) is a na-adjective. Na-adjectives behave like nouns. The word itself never changes — you conjugate だ/です after it, and you need な to put it in front of a noun.
Conjugation table
| Form | Plain (casual) | Polite (~です) | When you use it |
|---|---|---|---|
| Dictionary / plain | 水平だ suiheida | 水平です suiheidesu | The form you look up. Also the casual “is ~”. |
| Negative | 水平じゃない suiheijanai | 水平じゃないです suiheijanaidesu | “is not ~”. |
| Past | 水平だった suiheidatta | 水平でした suiheideshita | “was ~”. |
| Past negative | 水平じゃなかった suiheijanakatta | 水平じゃなかったです suiheijanakattadesu | “was not ~”. |
| Te-form | 水平で suiheide | — | Links to the next clause: “~ and …”. |
| Adverb | 水平に suiheini | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 水平な〜 suiheina〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 水平なら suiheinara | — | “if it is ~”. |
| Conditional (~たら) | 水平だったら suiheidattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 水平になる suiheininaru | 水平になります suiheininarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 水平すぎる suiheisugiru | 水平すぎます suiheisugimasu | “too ~”. |
| Looks ~ (~そう) | 水平そう suiheisou | 水平そうです suiheisoudesu | “looks / seems ~” from appearance. |
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Why it conjugates this way
Na-adjectives behave like nouns. The word itself never changes — you conjugate だ/です after it, and you need な to put it in front of a noun.
See the full rules in the adjective conjugation guide.