mental block vs inability

mental block and inability both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental block	Yes	No	No	No
inability	Yes	No	No	No

As nouns, inability is a hypernym of mental block; that is, inability is a word with a broader meaning than mental block:

mental block: an inability to remember or think of something you normally can do; often caused by emotional tension
inability: lack of ability (especially mental ability) to do something

mental block (noun)	inability (noun)
an inability to remember or think of something you normally can do; often caused by emotional tension	lacking the power to perform
	lack of ability (especially mental ability) to do something