Favourite is an adjective which means "most liked." Thus it can be used in the following possible sentences:
He is my favorite dog.
My favorite word is Austere
Example sentence - Her favorite subject in school is biology.
Capitulum is my favorite word.
The word favorite can be either an adjective or a noun.ExamplesIn the sentence:"Boofy was her favorite bear." it's an adjectiveIn the sentence:"Obama was the favorite to win the election." it's a noun.
A sentence using the word subject: My favorite subject in school was Science.
A sentence using the word rhubarb is, Strawberry rhubarb is my favorite kind of pie.
Example sentence - My favorite college class is zoology.
The lemon was our lease favorite.
tomorrow is my favorite day :)
This was the gourmets favorite restaurant.
Philosphy is my favorite subject.