retirement vs ending

retirement and ending both are nouns.

Word	Noun	Adjective	Verb	Adverb
retirement	Yes	No	No	No
ending	Yes	No	No	No

As nouns, ending is a hypernym of retirement; that is, ending is a word with a broader meaning than retirement:

Other hypernyms of retirement include conclusion, termination.

retirement (noun)	ending (noun)
withdrawal from your position or occupation	the act of ending something
withdrawal for prayer and study and meditation	the end of a word (a suffix or inflectional ending or final morpheme)
the state of being retired from one's business or occupation	the last section of a communication
	event whose occurrence ends something
	the point in time at which something ends