深い (fukai) conjugation
deep, profound
深い (ふかい, fukai) is an i-adjective. I-adjectives carry their own tense: drop the final い and the endings attach straight to the stem. No だ, no です needed to make a complete sentence.
Conjugation table
| Form | Plain (casual) | Polite (~です) | When you use it |
|---|---|---|---|
| Dictionary / plain | 深い fukai | 深いです fukaidesu | The form you look up. Also the casual “is ~”. |
| Negative | 深くない fukakunai | 深くないです fukakunaidesu | “is not ~”. |
| Past | 深かった fukakatta | 深かったです fukakattadesu | “was ~”. |
| Past negative | 深くなかった fukakunakatta | 深くなかったです fukakunakattadesu | “was not ~”. |
| Te-form | 深くて fukakute | — | Links to the next clause: “~ and …”. |
| Adverb | 深く fukaku | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 深い〜 fukai〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 深ければ fukakereba | — | “if it is ~”. |
| Conditional (~たら) | 深かったら fukakattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 深くなる fukakunaru | 深くなります fukakunarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 深すぎる fukasugiru | 深すぎます fukasugimasu | “too ~”. |
| Looks ~ (~そう) | 深そう fukasou | 深そうです fukasoudesu | “looks / seems ~” from appearance. |
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Why it conjugates this way
I-adjectives carry their own tense: drop the final い and the endings attach straight to the stem. No だ, no です needed to make a complete sentence.
See the full rules in the adjective conjugation guide.