Topic: Why dda rather than da in noswaith dda?

I am learning some Welsh using the free Duolingo.com course.

From early on I have been puzzled as to why dda rather than da in Noswaith dda.

Bore da Good morning
Prynhawn da Good afternoon
Noswaith dda Good evening
Nos da Good night

I now think that I have the answer, but it has raised another puzzle.

The answer, from studying

https://www.bbc.co.uk/bitesize/guides/z … revision/1

and

https://geiriadur.uwtsd.ac.uk/

is that Bore is masculine, Prynhawn is Masculine, yet Noswaith is Feminine, and so a soft mutation of da to dda happens.

Yet Nos is feminine, so why is it Nos da and NOT Nos dda?

William

Re: Why dda rather than da in noswaith dda?

I have now found the following.

https://www.reddit.com/r/learnwelsh/com … da_vs_dda/

William

Re: Why dda rather than da in noswaith dda?

A link in that thread leads to the following page.

https://en.m.wiktionary.org/wiki/Append … _mutations

William