Several parts combine into one character.

光 sets fire (火) above a person (儿) — a figure holding a torch over their head. The fire a person carries is "light." In the oracle bones a flame burns clearly above a kneeling figure.

Mandarin: guāng, level 1st tone. 光 (guāng, light), 阳光 (yángguāng, sunlight), 光明 (guāngmíng, brightness), 光荣 (guāngróng, glory), 眼光 (yǎnguāng, vision / discernment). It also means "used up, empty" — 花光了 (huāguāng le, spent it all).

Japanese: on-reading コウ (kō), kun ひかり (hikari) and ひか.る (hikaru). 光 (hikari, light), 日光 (nikkō, sunlight / the town Nikkō), 観光 (kankō, sightseeing), 光栄 (kōei, honor). The Shinkansen train named ひかり (Hikari) takes its name from this character.

Korean hanja-sound "gwang": 光線 (gwangseon, ray), 觀光 (gwangwang, sightseeing — "to see the light / culture"), 光復 (gwangbok, liberation — "the return of light"). The city 光州 (Gwangju) carries it too.

Memory aid: a fire (火) blazing above a person (儿) — a torch held overhead is "light."