(quatrain), a form of lyric poetry in the Middle East. It was adapted from the widespread oral folk poetry of the Persians and Tadzhiks, in which it is termed dubaiti or tarane. In written literature, the rubai, contrasting with the syllabic meter of folk poetry, is in the meter of aruz (an Arabic system of versification); it appeared in this form in the ninth and tenth centuries in the works of such poets as Rudaki. From that time, the rubai was invariably used for lyric poetry in which philosophic reflections predominated.

The rubai found its way from Persian literature into Arabic, Urdu, and many Turkic literatures. It reached its apogee as a genre in the mid-11th century but began yielding to the ghazal in the second half of the 12th century. The rubai consists of four hemistiches or two bayts, with a rhyme scheme of aaba and occasionally aaaa.