covariation vs variation

covariation and variation both are nouns.

Word	Noun	Adjective	Verb	Adverb
covariation	Yes	No	No	No
variation	Yes	No	No	No

As nouns, variation is a hypernym of covariation; that is, variation is a word with a broader meaning than covariation:

covariation (noun)	variation (noun)
(statistics) correlated variation	an activity that varies from a norm or standard
	the act of changing or altering something slightly but noticeably from the norm or standard
	(ballet) a solo dance or dance figure
	an artifact that deviates from a norm or standard
	something a little different from others of the same type
	a repetition of a musical theme in which it is modified or embellished
	an instance of change; the rate or magnitude of change
	(biology) an organism that has characteristics resulting from chromosomal alteration
	(astronomy) any perturbation of the mean motion or orbit of a planet or satellite (especially a perturbation of the earth's moon)
	the process of varying or being varied
	the angle (at a particular location) between magnetic north and true north