filter bed vs filter

filter bed and filter both are nouns.

Word	Noun	Adjective	Verb	Adverb
filter bed	Yes	No	No	No
filter	Yes	No	Yes	No

As nouns, filter is a hypernym of filter bed; that is, filter is a word with a broader meaning than filter bed:

filter bed: filter consisting of a layer of sand or gravel for filtering water
filter: device that removes something from whatever passes through it

filter bed (noun)	filter (noun)
filter consisting of a layer of sand or gravel for filtering water	device that removes something from whatever passes through it
	an electrical device that alters the frequency spectrum of signals passing through it

filter bed (verb)	filter (verb)
	remove by passing through a filter
	pass through
	run or flow slowly, as in drops or in an unsteady stream