Dialectal differences are very pronounced in the spoken and, to a lesser extent, the written language. A convenient, if slightly simplistic, classification is into North Walian and South Walian forms (or Gog and Hwntw based on the word for North, gogledd , and the South Walian word for "them over there"). The differences between dialects encompass vocabulary, pronunciation and grammar, although particularly in the last regard they are in fact fairly minor.
An example of the difference between North and South Walian usage would be the question "Do you want a cup (of tea)?" In the north this would typically be Dach chi isio panad? while in the south the question Dych chi moyn dishgled? would be more likely. An example of a pronunciation difference between Northern and Southern Welsh is the tendency in southern dialects to "lisp" the letter "s", e.g. mis (month), would tend to be pronounced [miːs] in the north, and [miːʃ] in the south. This normally occurs next to a high front vowel like /i/, although exceptions include the pronunciation of sut "how" as [ʃʊd] in the south (compared with northern [sɨt]). This is most likely the result of a change in the vowel quality.
Much more fine-grained classifications exist beyond north and south: the book Cymraeg, Cymrâg, Cymrêg: cyflwyno'r tafodieithoedd , about Welsh dialects was accompanied by a cassette containing recordings of fourteen different speakers demonstrating aspects of different dialects. The book refers to the earlier Linguistic Geography of Wales as describing six different regions which could be identified as having words specific to those regions. Another dialect is Patagonian Welsh, which has developed since the start of the Welsh settlement in Argentina in 1865; it includes Spanish loanwords and terms for local features, but a survey in the 1970s showed that the language in Patagonia is consistent throughout the lower Chubut valley and in the Andes and is basically the northern Welsh dialect (which is a little surprising as the majority of settlers came from the south, but the northern pronunciation seems to have been preferred — one settler recounted in his memoirs how he was marked down at the eisteddfod as a child for using southern diction).