A system of gears or the process of preparing for or adjusting to a particular situation or activity.
From gear, ultimately from Old Norse gervi (equipment). The mechanical sense developed in the 14th century, while the preparatory meaning emerged in the 20th century from the idea of 'shifting gears'.
Bicycle gears are a perfect example of mechanical advantage - by changing the size ratio between gears, you can trade speed for power or vice versa. It's the same principle that lets a tiny person open a heavy door with a long handle!
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