Yes, INFLEXION is a Scrabble word!

Letter values in Scrabble US: I 1, N 1, F 4, L 1, E 1, X 8, I 1, O 1, N 1.

Is it a valid word?

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

a change in the form of a word (usually by adding a suffix) to indicate a change in its grammatical function