buoyˈance (rare) or buoyˈancy noun

1. The capacity for floating or causing to float lightly on water or in the air
2. Loss of weight owing to immersion in a fluid
3. Lightness of spirit, cheerfulness, resilience

buoyˈant adjective

1. Tending to float or to buoy up
2. (of spirits, etc) light, cheerful and resilient
3. (of share prices, sales, profits, etc) tending to rise
4. (of a firm) with rising profits, etc

buoyˈantness noun

buoyancy aid noun

An inflated support for esp children learning to swim

buoyant density noun

The density of molecules, particles or viruses as determined by flotation in a suitable liquid