丁寧 (teinei) conjugation
polite, courteous, careful
丁寧 (ていねい, teinei) 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 | 丁寧だ teineida | 丁寧です teineidesu | The form you look up. Also the casual “is ~”. |
| Negative | 丁寧じゃない teineijanai | 丁寧じゃないです teineijanaidesu | “is not ~”. |
| Past | 丁寧だった teineidatta | 丁寧でした teineideshita | “was ~”. |
| Past negative | 丁寧じゃなかった teineijanakatta | 丁寧じゃなかったです teineijanakattadesu | “was not ~”. |
| Te-form | 丁寧で teineide | — | Links to the next clause: “~ and …”. |
| Adverb | 丁寧に teineini | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 丁寧な〜 teineina〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 丁寧なら teineinara | — | “if it is ~”. |
| Conditional (~たら) | 丁寧だったら teineidattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 丁寧になる teineininaru | 丁寧になります teineininarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 丁寧すぎる teineisugiru | 丁寧すぎます teineisugimasu | “too ~”. |
| Looks ~ (~そう) | 丁寧そう teineisou | 丁寧そうです teineisoudesu | “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.