A Ravenclaw is:
The emblem for Ravenclaw is the eagle and their house
colours are blue
The founder of Ravenclaw House is Rowena Ravenclaw.
The Ravenclaw ghost is Helena Ravenclaw, the daughter of Rowena Ravenclaw though the students of Hogwarts know her as the Grey Lady.
Rowena Ravenclaw's relic is Ravenclaw's diadem.