Several parts combine into one character.

煮 is a phonetic-semantic compound: 者 (zhě, "one who" — providing the sound, originally a depiction of stacked firewood) + 灬 (the four-dot fire radical, a horizontally-spread variant of 火 used at the bottom of compounds). The composite reads as "to set water boiling over fire" = to simmer, to boil, to cook in liquid. Together 焼 (grill / burn dry), 煮 (simmer / boil in liquid), and 蒸 (steam) cover the three basic East Asian cooking techniques, all marked by the fire radical 火/灬.

Korean reading "ja." Korean rarely uses 煮 in everyday speech: 煮沸 (jabi, boiling — formal scientific term used in 멸균 자비 sterilization), 煮繭 (jagyeon, "boiling silk cocoons" — sericulture term, the step of softening silk fibers). For "to boil / simmer," Korean overwhelmingly uses native (kkeurida) and (samkda).

Mandarin zhǔ, 3rd tone. 煮 (zhǔ, to boil / cook), 煮饭 (zhǔfàn, "to cook rice / make a meal"), 煮鸡蛋 (zhǔ jīdàn, boiled egg), 煮熟 (zhǔshú, "to boil until cooked"), 水煮 (shuǐzhǔ, water-boiled — used in 水煮鱼 shuǐzhǔ yú, the Sichuan dish "water-boiled fish in chili oil"). 煮 is everyday Mandarin cooking vocabulary.

Japanese on-reading シャ (sha) — 煮沸 (shafutsu, sterilization by boiling — medical term). Kun-reading にる (niru, "to simmer / boil") — 煮る (niru) is fundamental Japanese cooking vocabulary. The compound 煮物 (nimono, "simmered things") names an entire category of Japanese home cooking — vegetables, fish, and meats slow-simmered in dashi and soy sauce. Every Japanese home cookbook has a section on 煮物. 煮込み (nikomi, "stew / pot-cooked") describes long-simmered dishes like the famous Tokyo 牛すじ煮込み (gyūsuji nikomi, beef tendon stew). Japanese home cooking is built around niru.

Memory aid: 者 plus 灬 (four-dot fire) — placing a pot over fire = simmer / boil. Distinct from 焼 (dry grill) and 蒸 (steam).