They're usually interchangeable, but there can be a slight nuance. "Prohibited" implies that there's a written rule or law proscribing it, while "forbidden" could also mean that it's so far away from accepted norms that it's socially unacceptable. A synonym for that meaning of "forbidden" is "taboo."

Hi there. Yes, prohibited and forbidden are synonyms. That means they shared the same meaning but different words.

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