I understand that '(the) Welsh (language)' translates as y Gymraeg.
But in a previous exercise I had to translate 'Do you want to learn Welsh?', and I wrote:
Dych chi eisiau dysgu'r Gymraeg?
but this was wrong, the right answer being:
Dych chi eisiau dysgu Cymraeg?
According to Shwmae's comment, dysgu'r Gymraeg should have been accepted.
Now I'm a bit puzzled about the use of the article before Cymraeg , or the name of any other language.