1Splendid, fine, or lovely — a na-adjective used to praise something. In modern Japanese it appears mostly in polite set phrases such as 結構なお品 ('a fine gift').
結構なお品をいただき、ありがとうございます。
Thank you for the lovely gift.
お茶会で「結構なお点前でした」と挨拶した。
At the tea ceremony I said, "That was a splendid preparation of tea."
庭から海が見える、結構なお住まいですね。
You can see the sea from the garden — what a lovely home.
2Sufficient, satisfactory, fine, OK — a na-adjective used to indicate that something is enough or acceptable, as in これで結構です ('this is fine').
お支払いは現金で結構です。
Payment in cash is fine.
日程はこれで結構ですので、進めてください。
This schedule is fine, so please go ahead.
「サイズはこちらでよろしいですか？」「はい、結構です。」
"Is this size all right?" "Yes, that's fine."
3Used to decline — 'no more needed', 'no, thank you'. Common in もう結構です as a polite refusal. Because it overlaps with the 'that's fine (acceptance)' sense, tone and context distinguish the two.
「コーヒーのおかわりはいかがですか？」「いえ、もう結構です。」
"Would you like another cup of coffee?" "No, I'm fine, thank you."
ご丁寧な説明は結構です。要点だけ教えてください。
I don't need the detailed explanation; just tell me the main points.
その話はもう結構だ。聞きたくない。
That's enough of that story. I don't want to hear it.
4An adverb meaning 'quite', 'fairly', 'pretty', or 'more than expected'. Very common in speech, as in 結構いい ('pretty good') or 結構大変 ('quite tough').
この店のラーメン、結構おいしいよ。
The ramen at this place is pretty good.
駅から結構歩くから、早めに出よう。
It's quite a walk from the station, so let's leave early.
簡単そうに見えて、結構難しかった。
It looked easy, but it was actually quite hard.
彼、見た目によらず結構やさしいんだよ。
Despite how he looks, he's actually pretty kind.
5The structure or construction of a building or thing. An old, literary usage; modern Japanese normally uses 構造 instead.
古い寺院の結構は、当時の高度な建築技術を物語っている。
The structure of the old temple speaks to the advanced architectural techniques of the time.