Yes, UNITARY is a Scrabble word!

Letter values in Scrabble US: U 1, N 1, I 1, T 1, A 1, R 1, Y 4.

Is it a valid word?

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

relating to or characterized by or aiming toward unity
of or pertaining to or involving the use of units
characterized by or constituting a form of government in which power is held by one central authority
having the indivisible character of a unit