What is est ta matière when translated from French to English?

The phrase "est ta matière" is grammatically incorrect in French.

If you're looking for a translation of "Quelle est ta matière?", which means "What is your subject?" or "What is your subject matter?" then the English translation would be:

"What is your subject?" or "What is your subject matter?"

Let me know if you have any other phrases you'd like translated!