The word pinion has two separate meanings:

1. The outer part of a bird's wing, including the flight feathers. When a large bird like an eagle spreads its pinions and soars, you're watching those powerful wing sections catch the air.
2. A small gear wheel that fits into a larger one, working together to transfer motion in machines. Think of the gears inside a clock: the tiny pinion teeth mesh with bigger gear teeth, turning one gear's movement into another's. Without pinions, machines couldn't transfer power efficiently. You'll find pinions in car transmissions, bicycles, and countless other mechanical devices. Engineers carefully calculate the size and number of teeth on each pinion to get exactly the speed and power they need.