* Tú no eres: This is the informal "you" used for friends, family, and people you know well.
* Usted no es: This is the formal "you" used for strangers, someone older than you, or someone in a position of authority.
* Vos no sos: This is a common informal form used in some Latin American countries.
* Ustedes no son: This is the formal "you" used for multiple people.
You can also say:
* No eres: This is a more concise way to say "you are not" but it is less common than the other options.
* No sois: This is a more formal way to say "you are not" for multiple people.
Ultimately, the best way to say "you are not" in Spanish depends on the context and your relationship with the person you are talking to.