Le Tretiz ("Tractatus, i.e. liber manualis") est opusculum in versibus Francogallicis cum glossis Anglicis saeculo XIII medio a Gualtero de Bibbesworth scriptum, et saepius inter textus Anglonormannicos enumeratum. Liber Dionysiae de Monte Canisio dicatus ad instructione liberorum destinatus est, ut melius vocabula Francogallica de rebus rusticis et de vita quotidiana intellegerent. Gulielmus (filius eius) et Ioanna (filia mariti eius e prima uxore genita) ex hoc libro linguam Francogallicam didicisse censentur.
Thomas Wright, qui textum primus anno 1857 edidit, ita explicavit: "This "treatise" ... marks a very important period in the history of the English language, as it shows that before the end of the thirteenth century, and perhaps subsequently to the barons' wars, that language had already become the mother tongue of the children of the Anglo-Norman nobility, and that they learnt it before they were taught French".[1]