A lai (or lay lyrique, “lyric lay”, to distinguish it from a lai breton) 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. 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”).The terms note, nota and notula (as used by Johannes de Grocheio) appear to have been synonyms for lai.
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.
Source: Lai (poetic form) – Wikipedia