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warm; mild; (pleasantly) hot
こたつの中はぬくい。
It's warm inside the kotatsu.
今日は日差しがぬくかった。
The sunlight was warm today.
ぬくい布団から出たくなくて毎朝起きるのが大変だ。
I don't want to leave the warm futon, so getting up every morning is hard.