需要
じゅよう · juyou · JLPT N3 · noun
demand
🛒 需要 = need (需) + require (要): what buyers need and require = demand
Both kanji mean need: 需 is the need in 必需品 (necessities), 要 is the need in 必要 (necessary). Stacked, they give the economics term demand, paired with 供給 (kyoukyuu, supply). Sound hook: juyou ~ 'd'you want it?' — that is demand.
需 — rain 雨 + and 而
Originally a pictograph showing a person standing in the rain, meaning 'to wait' for the rain to stop. The bottom component 而 (originally depicting a beard or a standing figure) was later reanalyzed phonetically. The meaning shifted from 'wait' to 'need' or 'require,' while the older 'wait' sense was taken over by 須.
要 — west 覀 (top) + woman 女 (bottom)
Originally a pictograph of a woman with hands on her waist, meaning 'waist' (the original form of 腰). The top 覀 is a stylized depiction of the waist area, not the character for 'west'. Over time it was borrowed for the meaning 'to want, important', so 腰 (with 月 flesh radical) was created for the original 'waist' sense.