膨大 (boudai) conjugation
enormous, extensive
膨大 (ぼうだい, boudai) 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 | 膨大だ boudaida | 膨大です boudaidesu | The form you look up. Also the casual “is ~”. |
| Negative | 膨大じゃない boudaijanai | 膨大じゃないです boudaijanaidesu | “is not ~”. |
| Past | 膨大だった boudaidatta | 膨大でした boudaideshita | “was ~”. |
| Past negative | 膨大じゃなかった boudaijanakatta | 膨大じゃなかったです boudaijanakattadesu | “was not ~”. |
| Te-form | 膨大で boudaide | — | Links to the next clause: “~ and …”. |
| Adverb | 膨大に boudaini | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 膨大な〜 boudaina〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 膨大なら boudainara | — | “if it is ~”. |
| Conditional (~たら) | 膨大だったら boudaidattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 膨大になる boudaininaru | 膨大になります boudaininarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 膨大すぎる boudaisugiru | 膨大すぎます boudaisugimasu | “too ~”. |
| Looks ~ (~そう) | 膨大そう boudaisou | 膨大そうです boudaisoudesu | “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.