Yes, INCLINATION is a Scrabble word!

Letter values in Scrabble US: I 1, N 1, C 3, L 1, I 1, N 1, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

an attitude of mind especially one that favors one alternative over others
(astronomy) the angle between the plane of the orbit and the plane of the ecliptic stated in degrees
(geometry) the angle formed by the x-axis and a given line (measured counterclockwise from the positive half of the x-axis)
(physics) the angle that a magnetic needle makes with the plane of the horizon
that toward which you are inclined to feel a liking
the property possessed by a line or surface that departs from the vertical
a characteristic likelihood of or natural disposition toward a certain condition or character or effect
the act of inclining; bending forward

Also: inclination of an orbit, angle of inclination, angle of dip, magnetic dip, magnetic inclination.