Is there a prefix for forbidden?

There isn't a single, widely-used prefix specifically for "forbidden." However, depending on the context, you can use various prefixes to convey a similar meaning:

General prohibition:

* Un-: This prefix indicates the opposite of something, often used for forbidding actions. Example: "Unlawful," "unacceptable."

* Non-: This prefix means "not" and can be used for forbidden things or actions. Example: "Non-smoking," "non-alcoholic."

* Il-: This prefix means "not" or "against" and is often used in legal contexts. Example: "Illegal," "illicited."

Other prefixes:

* Anti-: This prefix means "against" and can be used to express opposition to something forbidden. Example: "Anti-social," "anti-government."

* Prohibited: This word itself can act as a prefix, meaning "not allowed." Example: "Prohibited area."

The best prefix to use depends on the specific context and the desired nuance. For example, "unlawful" implies a legal restriction, while "forbidden" might imply a moral or religious restriction.