"Christmas Day is the twenty-fifth of December."
Translation:Dydd Nadolig yw'r pumed ar hugain o Ragfyr.
Because we're linking two equivalents we need to use this construction.
eg. we say Barack Obama yw'r Arlywydd = Barack Obama is the President
but we can say Mae Barack Obama yn arlywydd = Barack Obama is a president.
so with Dydd Nadolig
Mae Dydd Nadolig yn ymlaciol = Christmas day is relaxing
Mae Dydd Nadolig yn dod = Christmas day is coming
Mae Dydd Nadolig ar y pumed ar hugain o Ragfyr = Christmas day is on the twenty fifth of December
Dydd Nadolig yw'r/ydy'r pumed ar hugain o Ragfyr.
I am very confused. In your example with President and Barack Obama, the two are equivalents, because you can reverse the word order and it makes perfect sense. But that isn't so with "relaxing" and "coming". But then you seem to say that the translation of "Christmas day is on the twenty fifth of December" is both "Mae Dydd Nadolig ar y pumed ar hugain o Ragfyr" and "Dydd Nadolig yw'r/ydy'r pumed ar hugain o Ragfyr", but you use the word BUT, to suggest there is a difference.
If we use the unemphatic pattern, the sentence starts with mae:
- Mae hi'n bwrw glaw
If we use the emphatic construction to emphasise a noun or an adjective, the verb is shifted along and we have to use ydy/yw instead:
- Dewi Lingo yw e
- Cryf yw Dewi
If we emphasise other elements we must still use mae:
- O Fangor mae Dewi'n dod heddiw
- Heddiw mae e'n dod
The emphatic construction is used in Welsh much more often than in English, as in the two examples of the date of Christmas day when ydy/yw is used in the middle of the sentence.
So in this case, the only reason for using yw instead of mae is to emphasise the date, which in English we'd instead probably indicate just with word stress?
The sentence about Christmas day is an equivalent sentence, you can swap the phrases round and it still makes sense.
Christmas day is the twenty fifth of December
The twenty fifth of December is Christmas day
ditto in Welsh
I was trying to point out the difference between this sentence and one beginning with 'mae' where it's not possible to swap them and still make sense.