Yes, MODES is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, D 2, E 1, S 1.

Is it a valid word?

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

how something is done or how it happens
a particular functioning condition or arrangement
a classification of propositions on the basis of whether they claim necessity or possibility or impossibility
verb inflections that express how the action or state is conceived by the speaker
any of various fixed orders of the various diatonic notes within an octave
the most frequent value of a random variable

Also: musical mode, modal value.