知己

to know oneself / to be intimate or close / intimate friend

to know / to be aware

self / oneself / sixth of the ten Heavenly Stems 十天干[shi2 tian1 gan1] / sixth in order / letter "F" or Roman "VI" in list "A, B, C", or "I, II, III" etc / hexa

know yourself, know your enemy (idiom, from Sunzi's "The Art of War" 孫子兵法|孙子兵法[Sun1 zi3 Bing1 fa3])

close friend in a distant land, far-flung realms as next door / close in spirit although far away

know yourself and know your enemy, and you will never be defeated (idiom, from Sunzi's "The Art of War" 孫子兵法|孙子兵法[Sun1 zi3 Bing1 fa3])

to know the enemy and know oneself (idiom, from Sunzi's "The Art of War")

knowing the enemy and yourself will get you unscathed through a hundred battles (idiom, from Sunzi's "The Art of War")

close female friend / confidante

close male friend / confidant

to consider sb as close friend (idiom); to take into one's confidence

a thousand cups of wine is not too much when best friends meet (idiom) / when you're with close friends, you can let your hair down

a true gentleman will sacrifice his life for a friend who understands him, as a woman makes herself beautiful for her sweetheart