hot water, bath, hot spring
湯 centers on heated water: hot water for bathing, a bath itself, or a natural hot spring. All meanings share the idea of water made warm for soaking or comfort.
湯 combines the water radical 氵 with 昜, which likely contributes the sound and may relate to warmth or rising. The character originally referred to hot water or heated liquid.
Water 氵 plus the warm-looking shape 昜 (like a sun 日 with spreading rays) suggests water heated by the sun: hot water for a bath or hot spring.
For トウ, imagine a toe dipping into hot water: toe -> トウ, and the warm bath soothes it.
hot water
hot water
public bath; bathhouse
boiling water
bathtub
steam; vapour; vapor
footbath; hot spring bath designed for soaking one's feet
tepid water; lukewarm water
white broth (esp. for ramen); broth without soy sauce (made by simmering bones)
(plain) hot water; boiled water
hot-water supply
hot-water bottle
steam
Chinese-style stir-fried vegetable noodle soup
women who assist bathers at hot-springs resorts
boiled tofu
hot-spring cure; taking the baths
source of a hot spring
tea ceremony; chanoyu
hot and cold water