Several parts combine into one character.

交 is a person with their two legs crossed in an X — the oracle bones clearly show a figure with crossed shins. From crossed legs grew "to cross, to intersect, to associate, to exchange."

Korean hanja-sound "gyo": 交通 (gyotong, traffic), 交流 (gyoryu, exchange), 外交 (oegyo, diplomacy), 交換 (gyohwan, exchange), 社交 (sagyo, social interaction), 交差 (gyocha, crossing). It enters everything where people cross paths and meet.

Mandarin: jiāo, 1st tone. 交通 (jiāotōng, traffic), 交流 (jiāoliú, exchange), 交朋友 (jiāo péngyou, to make friends), 交给 (jiāogěi, to hand over), 成交 (chéngjiāo, to close a deal). It also means "to hand in / submit" — 交作业 (to hand in homework).

Japanese: on-reading コウ (kō), kun まじ.わる (majiwaru) and か.わす (kawasu). 交通 (kōtsū, traffic), 交流 (kōryū, exchange), 交差点 (kōsaten, intersection), 交換 (kōkan, exchange), 交番 (kōban, police box). The Japanese street 交番 (kōban, police box) carries this character.

Memory aid: a person with legs crossed in an X — from crossing comes association and exchange.