Middle English describes dialects of English in the history of the English language between the High and Late Middle Ages, or roughly during the three centuries between the late 12th and the late 15th century.
Middle English developed out of Late Old English in Norman England (1066–1154) and was spoken throughout the Plantagenet era (1154–1485). The Middle English period ended at about 1470, when the Chancery Standard, a form of London-based English, began to become widespread, a process aided by the introduction of the printing press to England by William Caxton in the late 1470s. By that time the variant of the Northumbrian dialect (prevalent in Northern England) spoken in southeast Scotland was developing into the Scots language. The language of England as used after 1470 and up to 1650 is known as Early Modern English.
Unlike Old English, which tended largely to adopt Late West Saxon scribal conventions in the period immediately before the Norman conquest of England, written Middle English displays a wide variety of scribal (and presumably dialectal) forms. This diversity suggests the gradual end of the role of Wessex as a focal point and trend-setter for writers and scribes, the emergence of more distinct local scribal styles and written dialects, and a general pattern of transition of activity over the centuries that followed, as Northumbria, East Anglia, and London successively emerged as major centres of English literature, each with their own particular interests.
Middle English literature of the 12th and 13th centuries is comparatively rare, as written communication was usually in Anglo-Norman or in Medieval Latin. Middle English became much more important as a literary language during the 14th century, with poets such as Chaucer and Langland.
Important texts for the reconstruction of the evolution of Middle English out of Old English are the Ormulum (12th century), the Ancrene Wisse and the Katherine Group (early 13th century, see AB language) and Ayenbite of Inwyt (ca. 1340).