As a "langue d'oïl", Gallo forms part of a dialect continuum which includes Norman, Picard, and the Poitevin dialect among others. One of the features that distinguish it from Norman is the absence of Old Norse influence. There is some limited mutual intelligibility with adjacent varieties of the Norman language along the linguistic frontier and with Guernésiais and Jèrriais. However, as the dialect continuum shades towards Mayennais, there is a less clear isogloss. The clearest linguistic border is that distinguishing Gallo from Breton, a Brittonic Celtic language traditionally spoken in the western territory of Brittany.