Yes, DETERMINERS is a Scrabble word!

Letter values in Scrabble US: D 2, E 1, T 1, E 1, R 1, M 3, I 1, N 1, E 1, R 1, S 1.

Is it a valid word?

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

an argument that is conclusive
one of a limited class of noun modifiers that determine the referents of noun phrases
a determining or causal element or factor

Also: determining factor, causal factor.