Several parts combine into one character.

損 is a phonetic-semantic compound: 扌 (hand) + 員 (yuán, "personnel / round" — providing the sound). The composite reads as "to remove with the hand, to take away" = to reduce, damage, lose. 損 forms the canonical pair with 益 (yì, "to add / profit"): together they cover the financial balance sheet of gain and loss. Mainland simplified to 损.

Korean reading "son." 損失 (sonsil, loss — financial), 損害 (sonhae, damage — used both physically and legally: "compensation for damage"), 損益 (sonik, "loss-and-gain" = profit-and-loss; 손익계산서 = income statement), 破損 (pason, breakage / damage), 缺損 (gyeolson, deficit / shortage). Korean accounting vocabulary leans heavily on this character.

Mandarin sǔn, 3rd tone (simplified 损). 损失 (sǔnshī, loss), 损害 (sǔnhài, damage / harm), 亏损 (kuīsǔn, "deficit-loss" = financial deficit / running in the red), 破损 (pòsǔn, broken / damaged). 受损 (shòusǔn, "to suffer loss") is the standard verb for "to be damaged."

Japanese on-reading ソン (son) — 損失 (sonshitsu, loss), 損害 (songai, damage), 破損 (hason, breakage), 損得 (sontoku, "loss-and-gain" — colloquial for "pros and cons"). And 損 alone, read son, is used as a casual noun: それは損だ (sore wa son da, "that's a bad deal / that's losing out"). Kun-reading そこなう (sokonau, "to spoil / damage / harm") — 損なう (sokonau), and the related そこねる (sokoneru, "to ruin / mess up") — 機嫌を損ねる (kigen o sokoneru, "to spoil someone's mood / put them in a bad mood"), 健康を損なう (kenkō o sokonau, "to harm one's health"). The verbs are formal-register equivalents of casual speech.

Memory aid: hand (扌) plus 員 (just the sound) — the hand removing / taking away = loss. Pair with 益 (water overflowing the bowl = gain).