"I am Snape, the Potions master."
Severus Snape is the potions teacher. His nose is particularly big. Snape is hardly ever happy, and usually gets everyone in trouble.
He teaches potions class except in the short episode Martial Arts. (He teaches Defense against the Dark arts.) Sometimes he expresses his inner feelings. This was discovered in Snape's Diary where Harry finds his diary. Harry, Ron, and Hermione start to read Snape's entries. Snape seemed to be friends with Lucius Malfoy in one entry. Sad things were revealed to have happened to him in the diary. He used the "Avada Kedavra" spell in the animated series twice.