Originating in 10th-century Persian, a "ghazal" is a poetic form consisting of couplets that share a rhyme and a refrain. Formally, it consists of a short lyric composed in a single meter with a single rhyme throughout. The central subject is love. Notable authors include Hafiz, Amir Khusro, Auhadi of Maragheh, Alisher Navoi, Obeid e zakani, Khaqani Shirvani, Anvari, Farid al-Din Attar, Omar Khayyam, and Rudaki. The "ghazal" was introduced to European poetry in the early 19th century by the Germans Schlegel, Von Hammer-Purgstall, and Goethe, who called Hafiz his "twin".