bent vs knack

bent and knack both are nouns.

Word	Noun	Adjective	Verb	Adverb
bent	Yes	Yes	No	No
knack	Yes	No	No	No

As nouns, bent and knack are synonyms defined as:

Other synonyms of bent include hang.

bent (noun)	knack (noun)
a special way of doing something	a special way of doing something
a relatively permanent inclination to react in a particular way
an area of grassland unbounded by fences or hedges
grass for pastures and lawns especially bowling and putting greens

bent (adjective)	knack (adjective)
of metal e.g.
fixed in your purpose
used of the back and knees; stooped