grab vs obtain

grab is a noun but obtain is not a noun.

Word	Noun	Adjective	Verb	Adverb
grab	Yes	No	Yes	No
obtain	No	No	Yes	No

As verbs, obtain is a hypernym of grab; that is, obtain is a word with a broader meaning than grab:

grab (noun)	obtain (noun)
the act of catching an object with the hands
a mechanical device for gripping an object

grab (verb)	obtain (verb)
capture the attention or imagination of	receive a specified treatment (abstract)
take hold of so as to seize or restrain or stop the motion of	come into possession of
take or grasp suddenly	be valid, applicable, or true
make a grasping or snatching motion with the hand
get hold of or seize quickly and easily
obtain illegally or unscrupulously