(neuroanatomy) grey matter

central part or heart, especially of a city

brain / head / chief, principal

(neuroanatomy) white matter

the color white / (by extension) innocence / (go) a white go stone / something unwritten / (colloquial) the white team in a 紅白 (kōhaku) group / (colloquial) an unlicensed prostitute

quality

center, middle, heart, core (physical center) / center, hub (most important area of activity) / crux, main point

lye, originally the clear alkaline liquid left after leaching wood ash in water / scum, the coagulated proteins and fats that gather on the surface of a pot of boiling food

ash

beluga whale; white whale (Delphinapterus leucas)