A versatile particle serving multiple grammatical functions in Greek. Most commonly it introduces conditional clauses ('if'), where its regular negative is μή. It also introduces indirect questions ('whether'), where its negative is οὐ. In Homer it can serve as an interjection with imperatives ('come now!') or introduce wishes with the optative mood. With the optative, it expresses wishes—often unattained or unrealizable desires. With past tenses of the indicative, it can express contrary-to-fact conditions or unfulfilled wishes. The particle is fundamental to Greek syntax, enabling hypothetical reasoning, questions, and expressions of desire or regret.