Cornish is the British that developed in the extreme south west of the island.

There are three periods - old, middle and late Cornish. A glossary of the late 12th century has about 900 old Cornish words. Not one complete sentence survives from old Cornish. One sentence survives from the period before 1400. "In Polsethow ywhwylyr anethou"  (In Polsethow shall be seen dwellings).

Four texts survive from middle Cornish the latest of which dates 1504. Late Cornish is represented by texts from 1611 to 1707. The total amounts to less than 100,000 words, less than many a modern novel. Today the only rich source of information that remains is Cornish place and natural feature names. The last native speaker, Dolly Pentreath, died 1777.