Pictograph: a crossroads viewed from above — two intersecting paths forming an X / +. Where people meet and scatter, where lives intersect — that single visual became the verb "to go / to act / to operate". One of the most semantically loaded characters in the script. Identical across 繁體 / 新字体 / 简体.

行 is one of the legendary 破音字 (broken-tone characters) of the script — the SAME character carries multiple distinct meanings paired with distinct pronunciations.

Mandarin has TWO main readings: — xíng (rising 2nd tone): to walk / go / act / OK. 行人 (xíngrén, pedestrian), 进行 (jìnxíng, to carry out), 行动 (xíngdòng, action), 旅行 (lǚxíng, travel), 行 (xíng, "OK / fine"), 不行 (bùxíng, "no way / not OK"). The single-syllable colloquial "行" / "不行" is one of the most useful Mandarin words. — háng (rising 2nd tone): row / line / business. 银行 (yínháng, bank — "silver business"), 一行 (yīháng, one line of text), 行业 (hángyè, industry), 同行 (tóngháng, peers in same business — note: same characters as tóngxíng "to travel together", but different reading).

Japanese: TWO on-readings split by domain. — コウ (kō): 旅行 (ryokō, travel), 行動 (kōdō, action), 銀行 (ginkō, bank), 飛行機 (hikōki, airplane). — ギョウ (gyō): 行事 (gyōji, event / ceremony), 修行 (shugyō, ascetic practice), 行政 (gyōsei, administration), 一行 (ichigyō, one line of text). Kun-readings: い.く / ゆ.く (i.ku / yu.ku, to go) — the everyday verb; 行く先 (yukisaki, destination); おこな.う (okona.u, to perform / carry out — formal verb).

行く is one of the first verbs Japanese learners memorize. The OK/not-OK colloquial 行 is one of the first words Mandarin learners memorize. Same character, two foundational words.

Memory aid: a crossroads — every "going" radiates from intersections.