Yes, DERIVATIONS 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, O 1, N 1, S 1.

Is it a valid word?

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

the source or origin from which something derives (i.e. comes or issues)
(historical linguistics) an explanation of the historical origins of a word or phrase
a line of reasoning that shows how a conclusion follows logically from accepted propositions
(descriptive linguistics) the process whereby new words are formed from existing words or bases by affixation
inherited properties shared with others of your bloodline
drawing of fluid or inflammation away from a diseased part of the body
drawing off water from its main channel as for irrigation
the act of deriving something or obtaining something from a source or origin