graduation vs completion

graduation and completion both are nouns.

Word	Noun	Adjective	Verb	Adverb
graduation	Yes	No	No	No
completion	Yes	No	No	No

As nouns, completion is a hypernym of graduation; that is, completion is a word with a broader meaning than graduation:

Other hypernyms of graduation include closing, culmination, mop up, windup.

graduation (noun)	completion (noun)
the act of arranging in grades	a concluding action
the successful completion of a program of study	(American football) a successful forward pass in football
a line (as on a vessel or ruler) that marks a measurement
an academic exercise in which diplomas are conferred