* τρελός (trelos): This is a common and generally understood word for "crazy," often implying a lack of sanity or erratic behavior. It's a fairly neutral term.
* τρελαμένος (trelamenos): This is the past participle of "τρέχω" (trecho - to run) and means "driven mad," "insane," or "frenzied." It suggests a more intense form of craziness.
* παλαβός (palavos): This word implies foolishness and madness, often in a more whimsical or eccentric way than "trelos."
* ψυχικά άρρωστος (psixika arrostos): This literally translates to "mentally ill" and is a more formal and clinical term. It should only be used when appropriate.
* χαζός (chazos): This means silly or foolish, and while not directly translating to "crazy," it can be used informally to describe someone acting in a crazy or nonsensical way.
The best word to use will depend on the context. For most situations, τρελός (trelos) is a safe and widely understood option.