知己|ちきchiki[1]atamadaka (head-high)

1. nounacquaintance
   古ふるい知己ちきというものは、忘れ去わすれさられ、また一度いちども心こころに思い出おもいだされなくともよいのであろうか。↗

   Should old acquaintance be forgot, And never brought to mind?
2. nounclose friend

• Synonym知り合いしりあいNeutralThe most general word for a person you know. 「知己」 is more written and stresses a friend who truly understands you.
• Synonym知人ちじんNeutralA written-style word for an acquaintance. 「知己」 stresses deeper mutual understanding and closeness.
• Synonym顔見知りかおみしりNeutralA familiar face you nod to; the relationship stays shallow. 「知己」 usually means a close friend who understands you, though it can also cover mere acquaintances.
• Related仲間なかまNeutralFellows or companions you do things with; the bond is shared activity. 「知己」 is about knowing each other's hearts.
• Related朋輩ほうばいWrittenA written word for fellow students under the same teacher or colleagues at the same workplace; rarely used.
• Related知音ちいんWrittenA written word for a bosom friend who truly understands you, from the old tale of Boya and Ziqi; very close to 「知己」.
• Antonym他人たにんNeutralOther people or outsiders in general; contrasts with 「知己」 as a close friend who understands you.
• Antonym赤の他人あかのたにんNeutralSomeone wholly unconnected to you, with no kinship or real bond; it can even be said of a person you know. The direct opposite of 「知己」.

For an acquaintance, use 「知り合い」 or 「知人」; for companions you do things with, 「仲間」. 「知己」 usually means a true friend who really understands you, as in 「十年来の知己」, though it can also mean an acquaintance. A total stranger is 「赤の他人」.

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

1. 自分じぶんのことをよく理解りかいしてくれる人ひと。
2. 知人ちじん。知り合しりあい。