instal vs retrofit

instal is not a noun while retrofit is a noun.

Word	Noun	Adjective	Verb	Adverb
instal	No	No	Yes	No
retrofit	Yes	No	Yes	No

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

Other hyponyms of instal include reinstall, post, put up.

instal (noun)	retrofit (noun)
	the act of adding a component or accessory to something that did not have it when it was manufactured
	a component or accessory added to something after it has been manufactured

instal (verb)	retrofit (verb)
set up for use	substitute new or modernized parts or equipment for older ones
place	fit in or on an existing structure, such as an older house
put into an office or a position	provide with parts, devices, or equipment not available or in use at the time of the original manufacture