Yes, CRITERION is a Scrabble word!

Letter values in Scrabble US: C 3, R 1, I 1, T 1, E 1, R 1, I 1, O 1, N 1.

Is it a valid word?

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

a basis for comparison; a reference point against which other things can be evaluated
the ideal in terms of which something can be judged