Yes, VARIATION is a Scrabble word!

Letter values in Scrabble US: V 4, A 1, R 1, I 1, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

VARIATION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

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

Also: magnetic declination, magnetic variation, pas seul.