A lai is a lyrical, narrative poem written in octosyllabic couplets that often deals with tales of adventure and romance. Lais were mainly composed in France and Germany, during the 13th and 14th centuries. A Provençal term for a similar kind of poem is descort.
The English term lay is a 13th-century loan from Old French lai. The origin of the French term itself is unclear, perhaps it is itself a loan from German leich (reflected in archaic or dialectal English lake "sport, play").
Lais often have great metrical variety and are designed to be sung to a popular melody. One well-known author of Lais was Marie de France, whose collection of Lais (c. 1155-70) were twelve "Celtic" tales of romance that often involved elements of the fantastic. Lanval, one of her more popular narratives, is one such story. Marie de France’s lais came down to us in the same Norman dialect that was spoken in the court of Henry II (Angevin French king of England from 1154–89), to whom Marie dedicated her lais. For these reasons she is believed to have been a member of the court of Henry II. Marie claims to have translated her lais from the Breton language, and she later translated them into French. Though the works of male romancers during Marie’s time often focused on the need to balance personal needs and social responsibilities, Marie’s works have a strong female focus—especially on the personal desires of those female characters. Lanval, for example, is about a knight who is able to escape an uncaring and arbitrary society though the love of an otherworldly fairy figure. Thus, this lai portrays both the fantastic and female focus.
The poetic form of the lai usually has several stanzas, none of which have the same form. As a result, the accompanying music consists of sections which do not repeat. This distinguishes the lai from other common types of musically important verse of the period (for example, the rondeau and the ballade). Towards the end of its development in the 14th century, some lais repeat stanzas, but usually only in the longer examples. There is one very late example of a lai, written to mourn the defeat of the French at the Battle of Agincourt (1415), (Lay de la guerre, by Pierre de Nesson) but no music for it survives.
There are four lais in the Roman de Fauvel, all of them anonymous. The lai reached its highest level of development as a musical and poetic form in the work of Guillaume de Machaut; 19 separate lais by this 14th-century ars nova composer survive, and they are among his most sophisticated and highly-developed secular compositions.