What is "th-fronting"

Th-fronting refers to the pronunciation of the English "th" as "f" or "v". When th-fronting is applied, becomes (for example, three is pronounced as free) and becomes (for example, bathe is pronounced as bave). Unlike the fronting of to , the fronting of to doesn't occur in any dialect word-initially (for example, while bathe can be pronounced as bave, that is never pronounced as *vat). Th-fronting is a prominent feature of several dialects of English, notably Cockney, Estuary English, some West Country dialects, Newfoundland English, African American Vernacular English, and Liberian English, as well as in many foreign accents (though the details differ among those accents).