Alfred's Serif Users' Forums — Why dda rather than da in noswaith dda?

Re: Why dda rather than da in noswaith dda?

null@example.com (William) — Sun, 15 Sep 2024 12:44:46 +0000

A link in that thread leads to the following page.

William

null@example.com (William) — Sun, 15 Sep 2024 12:36:59 +0000

I have now found the following.

William

null@example.com (William) — Sun, 15 Sep 2024 12:29:58 +0000

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

and

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