Yes, DERIVATIVES is a Scrabble word!

Letter values in Scrabble US: D 2, E 1, R 1, I 1, V 4, A 1, T 1, I 1, V 4, E 1, S 1.

Is it a valid word?

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

the result of mathematical differentiation; the instantaneous change of one quantity relative to another; df(x)/dx
a compound obtained from, or regarded as derived from, another compound
a financial instrument whose value is based on another security
(linguistics) a word that is derived from another word

Also: derived function, differential coefficient, first derivative, derivative instrument.