prolong vs retain

prolong and retain both are verbs.

Word	Noun	Adjective	Verb	Adverb
prolong	No	No	Yes	No
retain	No	No	Yes	No

As verbs, retain is a hyponym of prolong; that is, retain is a word with a more specific, narrower meaning than prolong:

prolong: lengthen or extend in duration or space
retain: allow to remain in a place or position or maintain a property or feature

Other hyponyms of prolong include continue, keep, keep on.

prolong (verb)	retain (verb)
lengthen in time; cause to be or last longer	keep in one's mind
lengthen or extend in duration or space	secure and keep for possible future use or application
	allow to remain in a place or position or maintain a property or feature
	hold back within