rachet vs mechanical device

rachet and mechanical device both are nouns.

Word	Noun	Adjective	Verb	Adverb
rachet	Yes	No	No	No
mechanical device	Yes	No	No	No

As nouns, mechanical device is a hypernym of rachet; that is, mechanical device is a word with a broader meaning than rachet:

rachet: mechanical device consisting of a toothed wheel or rack engaged with a pawl that permits it to move in only one direction
mechanical device: mechanism consisting of a device that works on mechanical principles

rachet (noun)	mechanical device (noun)
mechanical device consisting of a toothed wheel or rack engaged with a pawl that permits it to move in only one direction	mechanism consisting of a device that works on mechanical principles