graduation vs gradation

graduation and gradation both are nouns.

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

As nouns, graduation and gradation are synonyms defined as:

graduation (noun)	gradation (noun)
the act of arranging in grades	the act of arranging in grades
the successful completion of a program of study	a degree of ablaut
a line (as on a vessel or ruler) that marks a measurement	relative position in a graded series
an academic exercise in which diplomas are conferred