"أي (Ay)" is an Arabic word that translates to "which" or "any" in English. It is commonly used in questions to specify a choice among options. For example, one might ask, "أي كتاب تفضل؟" which means "Which book do you prefer?" This word helps in clarifying preferences or selections in conversations. In Arabic grammar, "أي" can also function as an interrogative adjective. It is often used to introduce a noun and can be followed by a definite or indefinite noun. Understanding its usage is essential for effective communication in Arabic, especially in contexts involving choices or comparisons.