the ability or tendency of an object to float to the top of a body of liquid after being submerged in it;
e.g. The buoyancy of a volleyball or beach ball.
(noun)
the state or quality of cheerfulness, optimism or lightness; the ability to recover or bounce back quickly and easily from distress, depression, rejection, etc.;
e.g. Her buoyancy was a contributor to her success, as she continued to go to audition after audition until she was cast in a role.