seeder vs mechanical device

seeder and mechanical device both are nouns.

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

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

seeder: a mechanical device that sows grass seed or grain evenly over the ground
mechanical device: mechanism consisting of a device that works on mechanical principles

seeder (noun)	mechanical device (noun)
a kitchen utensil that removes seeds from fruit	mechanism consisting of a device that works on mechanical principles
a mechanical device that sows grass seed or grain evenly over the ground
a person who seeds clouds