情投意合

qíng tóu yì hé

to hit it off; to be well suited

Character by character

情qíng
feelings

投tóu
match

意yì
minds

合hé
agree

两个人情投意合，认识半年就结婚了。

They hit it off and were married within six months.

Tone: positive (praise).

Mostly of couples; for friends with shared goals 志同道合 is more usual.

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