Yes, BANANAS is a Scrabble word!

Letter values in Scrabble US: B 3, A 1, N 1, A 1, N 1, A 1, S 1.

Is it a valid word?

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

any of several tropical and subtropical treelike herbs of the genus Musa having a terminal crown of large entire leaves and usually bearing hanging clusters of elongated fruits
elongated crescent-shaped yellow fruit with soft sweet flesh

Also: banana tree.