けっこうです

When to use it

結構 means ‘fine, splendid’, and both uses grow from that.

1. Refusal. いいえ、けっこうです: no thank you, I have enough. Polite but firm, so soften it with ありがとうございます or a smile.
2. Approval. それでけっこうです / これでけっこうです: that will do, that is fine as it is. Typical from a superior or a customer.
3. Adverb. けっこう = quite, fairly: けっこう高い, けっこうおいしい.

Natives resolve the yes/no ambiguity by intonation, a hand gesture, or by choosing 大丈夫です (refusal) / お願いします (acceptance) instead.

Examples

• おかわりはいかがですか。— いいえ、けっこうです。ありがとうございます。（おかわり は いかが です か。— いいえ、けっこう です。ありがとう ございます）— Another helping? — No, thank you.
• 書類はこれでけっこうです。（しょるい は これ で けっこう です）— These documents are fine as they are.
• この店、けっこうおいしいね。（この みせ、けっこう おいしい ね）— This place is pretty good.

Traps for Spanish, English and French speakers

• ‘Está bien’, ‘ça va’ and ‘I’m good’ lead the same double life (yes, it’s fine / no, I’m fine), so the ambiguity feels familiar. What learners miss is that けっこうです leans toward no: to a shop assistant it is a refusal unless you add それで / これで. Spanish speakers who mean ‘vale, está bien’ and say けっこうです see the offer withdrawn.
• Learners who file けっこう under ‘no’ freeze when the boss says それでけっこうです. It is approval: your draft passed.
• Adverbial けっこう is ‘fairly, rather’, not ‘nicely’. けっこう高い is ‘pretty expensive’, a mild complaint, not ‘expensive but worth it’.
• The small っ matters: けこう is not a word. Hold the consonant as in Italian ‘ecco’.