Several parts combine into one character.

活 is a phonetic-semantic compound: 氵 (water) + 舌 (shé, "tongue" — providing the sound shé → huó). The composite reads as "moving like flowing water" = alive, vital, active. The metaphor is striking: life itself is conceived as flowing water — what does not flow is dead, what flows is alive. The water radical anchors not only physical-water characters but also abstract dynamic ones, with 活 sitting at the center as the great character of vitality.

Korean reading "hwal." 生活 (saenghwal, "alive-living" = daily life — used as the universal term for one's life situation: 학교생활 hakgyo saenghwal "school life"), 活動 (hwaldong, activity — used for organizational and social activities), 活力 (hwallyeok, vitality / vigor), 活氣 (hwalgi, energy / liveliness), 復活 (buhwal, "revived life" = resurrection / revival — both Christian Easter context and metaphorical), 活用 (hwaryong, "vital use" = practical application / making active use of). Korean 생활 is a fundamental noun for "life" in everyday speech.

Mandarin huó, 2nd tone. 活 (huó, alive / to live), 生活 (shēnghuó, life — the everyday word, identical compound to Korean 생활), 干活 (gànhuó, "to do living" = to work / do labor — colloquial), 灵活 (línghuó, "spirit-alive" = flexible / nimble / adaptable — top-frequency adjective in Mandarin), 活动 (huódòng, activity / event), 死活 (sǐhuó, "death-life" = "life or death / no matter what"). 灵活 is one of the most useful adjectives for describing thinking style, schedule flexibility, and physical agility.

Japanese on-reading カツ (katsu) — 生活 (seikatsu, life), 活動 (katsudō, activity), 復活 (fukkatsu, revival — used both religiously and casually), 活用 (katsuyō, practical application / utilization), 活気 (kakki, energy / vitality — used to describe lively atmospheres: 活気のある街 kakki no aru machi, "a lively neighborhood"). 活 has essentially no kun-reading; the on-reading カツ dominates. 就活 (shūkatsu, "job-hunting" — abbreviation of 就職活動 shūshoku katsudō) became a major Japanese cultural term referring to the senior-year ritual of mass corporate recruiting.

Memory aid: water (氵) flowing like a tongue (舌) — flowing motion = being alive.