filter vs filter out

filter is a noun but filter out is not a noun.

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

As verbs, filter and filter out are synonyms defined as:

Other synonyms of filter include filtrate, separate out, strain.

filter (noun)	filter out (noun)
device that removes something from whatever passes through it
an electrical device that alters the frequency spectrum of signals passing through it

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