Axle: The shaft in the middle of the two yo-yo halves is the axle.

Clutch Return: During the sleep, weights inside the yo-yo push up against springs in the yo-yo. When the yo-yo slows down, the clutch pops and the yo-yo comes back up.

Favorite hand: The hand you use your yo-yo with, or write with, is your favorite hand. Your unfavorite hand is the hand you don’t use your yo-yo with or write with.

Fixed Axle: The two halves connected by the axle spin as a unit.

Sleeping: The yo-yo spins down at the bottom of the string without the yo-yo coming up (until you flick your wrist).