An interrogative phrase (written as two words: διὰ τί) meaning 'why?' or 'for what reason?' The construction literally asks 'on account of what?' using the preposition διὰ with the interrogative pronoun τί. It introduces questions seeking explanation, cause, or rationale for an action or state of affairs. The phrase functions as a standard way to inquire about reasons or purposes, appearing frequently in dialogue and rhetorical questions throughout Greek literature.