Welsh is a Brythonic Celtic language, quite-closely related to the Cornish and Breton languages. Welsh also shares a "P-Celtic" connection to some now extinct Celtic languages on the continent, including Gaulish, a Celtic language with a more classic Indo-European and, in extension, Latin-like noun declination system.

Welsh also shares some kind of relationship to some of the ancient languages spoken in England and Scotland, usually themselves being identified as other Brythonic or P-Celtic languages, namely "Southwestern Brittonic", connected to southwest England as a whole, "Cumbric" connected to northern England and Southern Scotland, and "Pictish", connected to eastern Scotland. In truth, I think it was far more complex than this, and that these aforementioned languages have been somewhat misidentified, and there is I think a lot of reasoning behind this, but I've discussed this elsewhere, and this article is meant to be more of an in-depth introduction to Welsh, not the entire background of the language. 

Welsh has four main dialects, Northwestern Welsh, Northeastern Welsh, Southwestern Welsh and Southeastern Welsh. The exact titles of and classification of these dialects can be quite fluid, but there are also different registers of Welsh depending on context and formality. For example, the Northeastern dialects of Welsh are nearly extinct, whilst the southeastern varieties are already extinct as a first language, and instead, some books will teach "North Welsh" or "South Welsh" as general, non-localised "forms" of Welsh in the north and Welsh in the south, respectively, which will not contain more specific localised features to certain areas. 

Welsh also has different registers in terms of formality, and more formal contexts often mean using "Literary Welsh", a form of the Welsh language, which also has some dialectal differences across Wales, but which is, grammatically speaking, much more akin to the Middle Welsh language of the Medieval period (and earlier?) than it is to the modern Colloquial Welsh forms of language. More about this later. 

In this article, I focus on a general form of North Welsh, which today, means a form of Welsh having the closest similarity to the dialects of northwest Wales, including those spoken within Parc Cenedlaethol Eryri - "Snowdonia National Park", Llŷn - "The Lleyn Peninsula", and Môn - "Anglesey". In this article, I will give in depth examples of the language and how it works, as well as giving context to its cultural and mythological backgrounds - both of which are invariably entwined with and within the language itself.