General:
* Quelque chose de nouveau: This is the most literal translation and means "something new".
* Une nouveauté: This means "a novelty" and emphasizes the newness of the thing.
* Une nouvelle: This means "a new thing" and is more formal than "quelque chose de nouveau".
Specific contexts:
* Une nouvelle idée: "A new idea"
* Un nouveau produit: "A new product"
* Une nouvelle expérience: "A new experience"
* Un nouveau départ: "A new start"
* Un nouveau chapitre: "A new chapter"
You can also use the adjective nouveau (new) before a noun:
* Un livre nouveau: "A new book"
* Une voiture nouvelle: "A new car"
The best way to choose the right expression depends on the specific situation.
For example, if you are talking about a new idea, you would say "une nouvelle idée". If you are talking about a new product, you would say "un nouveau produit".
Remember to consider the context and the nuance you want to convey when choosing your words.