French phrase
Je suis étudiant en ~.
Meaning
I'm a ___ student.
When to use it
States a person's field of study. It is natural in everyday self-introductions and has a neutral level of politeness.
Example dialogue
Je suis étudiant en informatique.
I'm a computer science student.
Ah bon ? Tu fais quoi comme cours ?
Oh, really? What classes are you taking?