点く
つく · tsuku · JLPT N4 · verb-godan
to be switched on
💡 tsuku: the light TSUcKs into its socket and comes on
点 means a dot or point, and also to light. 点く is the intransitive partner of 点ける (to switch on): the lamp or TV comes on by itself. 電気が点く = the light comes on. Same sound as 付く (to attach) — power attaches, device runs.
点 — fire radical 灬 + 占 (zhān, phonetic)
Originally written 點, a semantic-phonetic compound: 黑 (black) gave the meaning 'small black mark or dot' while 占 supplied the sound. It first referred to ink spots, then extended to 'point, drop, a little,' and verbs like 'to mark' or 'to light (a fire),' reflected in the simplified form's 灬 (fire) component.