T is for:

TIME-TURNER: Now banned and destroyed by the ministry. However they used to be fairly common practice to allow students to do more than the regular amount of classes.

TONKS: Edward Tonks was a muggle-born wizard sorted in to Hufflepuff. He married Andromeda Black, a Pureblood Slytherin and they had Nymphadora Tonks who was also sorted into Hufflepuff.

TRANSFIGURATION: My favourite subject. (what else). The transformation of a being into a different looking being.

TROLLS: Large smelly creatures that are dumb and usually live in caves.