Dyn ni'n cau'r siop, a very southern way of saying things! A better way would be to say "Ryda ni'n cau'r siop" so to be useful in the north and south of wales. Or, "Da ni'n cau'r siop" which is what I would say as a Welsh speaker from Anglesey
They introduced "Dan ni" as an alternative to "Dyn ni" in the unit on dialects. You're right, I haven't seen it since then though.
I wouldn't call it a 'very' southern way. That would be "(R)y'n ni'n cau'r siop" or "(R)y'n ni'n cïed y siop" even!
Never heard of "cied" before! Yn lle ma pobol yn deud hyna? Yn yr hen Gymraeg?
there is a bug here. it says "cau'r" is a new word but it doesn't show the meaning.
"Cau'r" comes from "cau yr/cau y" - and "cau" is the verb "to close"
The "yr/y" depends on the noun being a vowel or a consonant, e.e "Y Byd" (The World) and "Yr Afal" (The Apple)
Yr before h too, and consonantal i but not consonantal w. So: yr haf (the summer), yr iâr (the chicken) but y wal (the wall).