工 is a picture of a craftsman's tool — the top and bottom horizontals are the head and base, the vertical is the handle. The leading reading is a carpenter's set-square (a right-angle ruler). "The one who holds the measuring tool" gave us, from a single implement, the meanings craftsman, labor, and work.

Mandarin: gōng, level 1st tone. 工作 (gōngzuò, work / job), 工人 (gōngrén, worker), 工程 (gōngchéng, engineering project), 打工 (dǎgōng, to work a part-time job). The core vocabulary of modern Chinese society begins with 工.

Japanese: on-readings コウ (kō) and ク (ku); essentially no kun-reading. 工場 (kōjō, factory), 工夫 (kufū, ingenuity / contrivance), 大工 (daiku, carpenter). A nice cross-language trap: the compound 工夫 means "study" in Korean (gongbu) but "ingenuity" in Japanese (kufū).

Korean hanja-sound "gong": 工場 (gongjang, factory), 人工 (ingong, artificial), 施工 (sigong, construction work). This very site, 施工式 (sigongsik), carries this 工 in its name.

As a component it also lends its sound: 紅 (hóng, red), 江 (jiāng, river), 空 (kōng, empty), 功 (gōng, merit) all borrow the phonetic 工.

Memory aid: a handle joining a top and bottom stroke — a single tool in an artisan's grip.