Several parts combine into one character.

眠 is a phonetic-semantic compound: 目 (eye) + 民 (mín, "people / populace" — providing the sound mín → mián / min / myeon). The composite reads as "to close the eyes" — to slumber. 眠 forms a meaningful pair with 寝 (sleep): 寝 is the action of going to bed, while 眠 is the state of being asleep. The two characters together cover the full arc of sleep behavior.

Korean reading "myeon." 睡眠 (sumyeon, sleep — formal medical term), 安眠 (anmyeon, peaceful sleep — used in pharmaceutical names like 안면제 sleeping aid), 冬眠 (dongmyeon, hibernation), 不眠症 (bulmyeonjeung, insomnia), 熟眠 (sungmyeon, deep sleep), and the literarily charged 永眠 (yeongmyeon, "eternal sleep" = death — used as a euphemism in formal obituaries).

Mandarin mián, 2nd tone. 失眠 (shīmián, "lose-sleep" = insomnia — extremely common term in modern Chinese health discussions), 睡眠 (shuìmián, sleep), 冬眠 (dōngmián, hibernation), 安眠药 (ānmiányào, sleeping pill). Modern Chinese keeps 眠 active in medical and biological contexts.

Japanese on-reading ミン (min) — 睡眠 (suimin, sleep), 安眠 (anmin, peaceful sleep), 冬眠 (tōmin, hibernation), 永眠 (eimin, eternal sleep / death — same euphemistic use as Korean). Two kun-readings differentiate states: 眠い (nemui, "sleepy" — the felt drowsy state) and 眠る (nemuru, "to fall asleep" — entering unconsciousness). Critically, Japanese carefully distinguishes 眠る (nemuru, the state of being asleep) from 寝る (neru, the action of going to bed). 早く寝なさい ("go to bed early") is the parental command; 早く眠れない ("I can't fall asleep quickly") is the insomniac's complaint. Same general topic, different verbs.

Memory aid: eyes (目) closing as one, like the populace (民) settling down — sleep.