Several parts combine into one character.

池 is a phono-semantic character: 水 (氵, water) carries the meaning, 也 lends the sound. Water that gathers and stays in one place — a pond or pool. 也 only lends the sound "chí/ji"; it has nothing to do with the meaning.

Mandarin: chí, 2nd tone. 池塘 (chítáng, pond), 游泳池 (yóuyǒngchí, swimming pool), 电池 (diànchí, battery), 水池 (shuǐchí, basin). The word 电池 (battery) is vivid — electricity in a "gathering pool."

Japanese: on-reading チ (chi), kun いけ (ike). 池 (ike, pond), 電池 (denchi, battery), 貯水池 (chosuichi, reservoir), 古池 (furuike, old pond) — from Bashō's famous haiku "the old pond, a frog jumps in, the sound of water." The pond is a central element of the Japanese garden.

Korean hanja-sound "ji": 貯水池 (jeosuji, reservoir), 電池 (jeonji, battery), 天池 (Cheonji, the crater lake atop Mount Baekdu), 蓮池 (yeonji, lotus pond).

Memory aid: water (氵) that gathers and stays — water collected in one place rather than flowing away.