prehension vs grasp

prehension and grasp both are nouns.

Word	Noun	Adjective	Verb	Adverb
prehension	Yes	No	No	No
grasp	Yes	No	Yes	No

As nouns, grasp is a hyponym of prehension; that is, grasp is a word with a more specific, narrower meaning than prehension:

prehension: the act of gripping something firmly with the hands (or the tentacles)
grasp: the act of grasping

Other hyponyms of prehension include clasp, clench, clutch, clutches, grip, hold.

prehension (noun)	grasp (noun)
the act of gripping something firmly with the hands (or the tentacles)	the act of grasping
	an intellectual hold or understanding
	understanding of the nature or meaning or quality or magnitude of something
	the limit of capability

prehension (verb)	grasp (verb)
	get the meaning of something
	hold firmly