退屈 (taikutsu) conjugation
tedium, boring
退屈 (たいくつ, taikutsu) 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 | 退屈だ taikutsuda | 退屈です taikutsudesu | The form you look up. Also the casual “is ~”. |
| Negative | 退屈じゃない taikutsujanai | 退屈じゃないです taikutsujanaidesu | “is not ~”. |
| Past | 退屈だった taikutsudatta | 退屈でした taikutsudeshita | “was ~”. |
| Past negative | 退屈じゃなかった taikutsujanakatta | 退屈じゃなかったです taikutsujanakattadesu | “was not ~”. |
| Te-form | 退屈で taikutsude | — | Links to the next clause: “~ and …”. |
| Adverb | 退屈に taikutsuni | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 退屈な〜 taikutsuna〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 退屈なら taikutsunara | — | “if it is ~”. |
| Conditional (~たら) | 退屈だったら taikutsudattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 退屈になる taikutsuninaru | 退屈になります taikutsuninarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 退屈すぎる taikutsusugiru | 退屈すぎます taikutsusugimasu | “too ~”. |
| Looks ~ (~そう) | 退屈そう taikutsusou | 退屈そうです taikutsusoudesu | “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.