Diglossia is a sociolinguistic phenomenon where two dialects or languages coexist within a single community, each serving distinct functions: a high (H) variety for formal situations and a low (L) variety for informal communications. Originating from the 1959 work of Charles A. Ferguson, the concept encompasses various features like language prestige, acquisition methods, and stability across different societies. The document details examples of diglossia, particularly highlighting the distinctions between Urdu and English, and Punjabi and Urdu within Pakistan, emphasizing their functional, prestige, and educational differences.