noun
ratchet; toothed wheel
A mechanical wheel with teeth that allows motion in one direction only, often used with a pawl. Technical term.
See also: ラチェット
この工具には爪車が使われている。
This tool uses a ratchet.
爪車が故障すると、逆回転してしまう。
If the ratchet fails, it will rotate backwards.
ラチェット is a loanword from English 'ratchet', often used for the mechanism or tool, while 爪車 is the native Japanese term emphasizing the toothed wheel component.
Compound of 爪 (つめ, 'claw, pawl') and 車 (くるま, 'wheel'), describing a wheel with claw-like teeth.