Three characteristics that are unique to mammals include their  ability to feed their babies with milk made in their mammary  glands. Mammals also have hair on their bodies â¦and they have a  single bone that makes up their lower jaw.
buoyancy. n. 1. the ability to float in a liquid or to rise in a fluid. 2. (General Physics) the property of a fluid to exert an upward force (upthrust) on a body that is wholly or partly submerged in it. 3. the ability to recover quickly after setbacks; resilience.
Regardless of the fluid in which an object is immersed (gas or liquid), the buoyant force on an object is equal to the weight of the fluid it displaces. A hot air balloon when it has neutral buoyancy has no weight for the men to support but still retains its great mass and inertia.