Several parts combine into one character.

蒸 is a phonetic-semantic compound: 艹 (grass / plant) + 烝 (zhēng, "to steam / vapor rising"). The phonetic 烝 is itself an ideograph showing steam rising from fire below, perfectly capturing the steaming action. The grass radical 艹 was added to specify "to steam grain or plants" — referring to the use of bamboo steamers over boiling water, which became the foundational technique for Chinese dim sum, Japanese sekihan rice, and countless other steamed dishes.

Korean reading "jeung." 蒸氣 (jeunggi, steam / vapor — physics term), 蒸發 (jeungbal, evaporation — chemistry / weather term), 蒸留水 (jeungnyusu, distilled water), 水蒸氣 (sujeunggi, water vapor), 蒸饅頭 (jeungmandu, steamed dumpling — Korean banquet dish, dough wrapping savory filling, similar to Chinese baozi). Korean cooking terms include (jjim, steaming as a cooking method, native word), with 증류 / 증발 used in scientific contexts.

Mandarin zhēng, 1st tone. 蒸 (zhēng, to steam), 蒸气 (zhēngqì, vapor), 蒸饺 (zhēngjiǎo, "steam-dumpling" = steamed dumpling), 蒸笼 (zhēnglóng, "steam-cage" = bamboo steamer basket, the iconic stacked round baskets used in dim sum), 清蒸 (qīngzhēng, "clean / pure steaming" = a Cantonese style emphasizing fresh light steaming, as in 清蒸鱼 qīngzhēng yú "Cantonese steamed fish" — a famous restaurant dish that lets the freshness of seafood shine through).

Japanese on-reading ジョウ (jō) — 蒸気 (jōki, steam — used for steam locomotives 蒸気機関車 jōki kikansha), 蒸発 (jōhatsu, evaporation — and metaphorically: "to disappear without trace" / "to abscond" — a person who has 蒸発 した has vanished from their family and life), 蒸留 (jōryū, distillation). Kun-reading むす (musu, "to steam") — 蒸す (musu) — and the wonderful 蒸し暑い (mushiatsui, "steam-hot" = humid and stifling — Japan's notoriously humid summers are described with this exact word, equivalent to "muggy" in English). 茶碗蒸し (chawanmushi, "tea-bowl-steamed" = savory egg custard, a delicate Japanese kaiseki dish made by steaming beaten egg, dashi, and small ingredients in a tea bowl).

Memory aid: grass / grain (艹) plus steam rising from fire (烝) — applying steam = the third great cooking technique alongside 焼 and 煮.