快い・心良い|こころよいkokoroyoi[4]nakadaka (mid-high)

1. i-adjectivepleasant; agreeable; comfortable; refreshing
   私は昨夜さくや快こころよく眠ねむった。↗

   I slept comfortably last night.

• Synonym心地よいここちよいNeutralDescribes comfort from things like wind or sound much like 「快い」; the two are interchangeable, but only 「快い」 can mean gladly agreeing, as in 「快く引き受ける」.
• Synonym快適かいてきNeutralDescribes comfortable surroundings, facilities or trips, as in 「快適な部屋」, and is common in both speech and writing; 「快い」 leans toward a refreshing feel.
• Synonym気持ちいいきもちいいCasualThe most common colloquial word for feeling good physically, as in 「気持ちいい朝」; 「快い」 is more refined and mostly seen in writing.
• Synonym愉快ゆかいNeutralMeans cheerful or amusing, as in 「愉快な仲間」; it mostly describes people or an atmosphere, while 「快い」 describes the feeling itself.
• SynonymいいCasualThe colloquial form of 「良い」, just as broad; it comes close to 「快い」 when it describes a pleasant feeling, as in 「気持ちがいい」.
• Related良いよいNeutralA general word for good, fine or sufficient, far broader than 「快い」; it only comes close when used to mean pleasant.
• Related好ましいこのましいWrittenA written-style word for something desirable or viewed favorably, as in 「好ましい結果」; it is an evaluation, not about physical or sensory comfort.
• Related嬉しいうれしいNeutralExpresses the joy of having a wish fulfilled, as in 「嬉しい知らせ」; 「快い」 is more about the pleasant feel of outside stimuli.
• Related満足まんぞくNeutralMeans contentment when desires are met, also as 「満足する」; it is about needs being satisfied, not the comfort of a breeze or sound.
• Related気楽きらくNeutralMeans carefree and unburdened, as in 「気楽な生活」; it is about having few worries, not sensory pleasure.
• Related喜ばしいよろこばしいWrittenDescribes welcome news or events worth rejoicing over, as in 「喜ばしいニュース」; mostly written or formal speeches, and not about bodily comfort.
• Related楽しいたのしいNeutralFor fun, enjoyable activities or experiences, as in 「楽しい旅行」; it stresses fun, while 「快い」 stresses a refreshing, comfortable feel.
• Related気安いきやすいNeutralDescribes being relaxed and familiar with people, as in 「気安く話しかける」; it is about human relations, with no link to sensory comfort.
• Antonym気持ち悪いきもちわるいCasualColloquial antonym for feeling sick or finding something gross or creepy; it stands opposite the comfort of 「気持ちいい」 and 「快い」.
• Antonym不快なWrittenAntonym: means unpleasant or uncomfortable, as in 「不快な臭い」; it is the direct opposite of the comfort of 「快い」, with a slightly formal tone.

For everyday 'feels good' talk, 「気持ちいい」 is the default; for comfortable rooms, facilities or trips use 「快適」. Choose 「快い」 in written prose or for gladly agreeing, as in 「快く引き受ける」. 「嬉しい」 is joy at a wish fulfilled, 「楽しい」 fun, 「満足」 contentment, 「気楽」 being carefree.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 外界がいかいからの刺激しげき、情報じょうほうなどが気持きもちよく感かんじられる。
2. 病気びょうきがよくなる様子ようすだ。