Buoyancy (noun)

1. The ability or tendency to float on a liquid or in air.
2. The upward force that keeps a floating object afloat.

Origin:

From the middle french word 'boyance' meaning 'floating', from the latin word 'buoyare' meaning 'to float'.

Examples:

1. The buoyancy of the life jacket kept the swimmer afloat in the water.
2. The design of the boat depends on the relationship between its weight and buoyancy.
3. Hot air balloons are kept aloft by the buoyancy of the heated air inside the envelope.
4. The astronaut demonstrated how to use the suit's buoyancy to control their movement in space.
5. The fish's swim bladder helps regulate its buoyancy and allows it to swim at different depths.