頑固 (ganko) conjugation
stubbornness, obstinacy
頑固 (がんこ, ganko) 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 | 頑固だ gankoda | 頑固です gankodesu | The form you look up. Also the casual “is ~”. |
| Negative | 頑固じゃない gankojanai | 頑固じゃないです gankojanaidesu | “is not ~”. |
| Past | 頑固だった gankodatta | 頑固でした gankodeshita | “was ~”. |
| Past negative | 頑固じゃなかった gankojanakatta | 頑固じゃなかったです gankojanakattadesu | “was not ~”. |
| Te-form | 頑固で gankode | — | Links to the next clause: “~ and …”. |
| Adverb | 頑固に gankoni | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 頑固な〜 gankona〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 頑固なら gankonara | — | “if it is ~”. |
| Conditional (~たら) | 頑固だったら gankodattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 頑固になる gankoninaru | 頑固になります gankoninarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 頑固すぎる gankosugiru | 頑固すぎます gankosugimasu | “too ~”. |
| Looks ~ (~そう) | 頑固そう gankosou | 頑固そうです gankosoudesu | “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.