matter of course vs ending

matter of course and ending both are nouns.

Word	Noun	Adjective	Verb	Adverb
matter of course	Yes	No	No	No
ending	Yes	No	No	No

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

Other hypernyms of matter of course include conclusion, finish.

matter of course (noun)	ending (noun)
an inevitable ending	the act of ending something
	the end of a word (a suffix or inflectional ending or final morpheme)
	the last section of a communication
	event whose occurrence ends something
	the point in time at which something ends