Water radical 氵 sits on the left of every wash-action character - 洗 (wash), 浴 (bathe), 涮 (rinse), 漱 (gargle). Three drops, then 先 for the sound.
register
Almost always read xǐ. A second reading xiǎn survives in exactly one frozen compound: 洗马, an archaic imperial title (herald to the crown prince). You will never need xiǎn in modern speech - every compound in this dictionary uses xǐ.
Left-side three-drop water radical, indexing component. Marks 洗 as a water action - washing, rinsing, cleaning. Same radical anchors 浴 (bathe), 涮 (rinse), 漱 (gargle), 泡 (soak).
Right-side 先 supplies the sound: xiān shifts to xǐ with a tone change. A faint semantic echo - washing is often the first step before eating or working - but the role is primarily phonetic. Same xiān series: 跣 (bare feet), 铣 (mill).
