This is a question from a dialogue:
“Be oedd ar y teledu neithiwr?” = What was on the television last night?
The given answer is: “Mi oedd Pobol y Cwm ar y teledu neithiwr.”
I’m not sure I understand Mi oedd.
I get that it’s saying “Pobol y Cwm was on the television last night” but could the answer also be, “Roedd Pobol y Cwm ar y teledu neithiwr?” which is how I would have answered it instead of Mi oedd.
(I’m also not always sure when to use, o’n i and mi wnes i.)
The ‘mi’ here is just an indicator of a positive statement (it’s Southern variant is to put ‘fe’ there instead). It’s used in some dialects and not in others, so yes, you could equally answer “Roedd Pobol y Cwm ar y teledu neithiwr”.
As for o’n i, that is a further shortening of oedd, but in the first person ( i ) - Other pronouns have shortenings like this too: ti = o’t ti, chi = o’ch chi, ni = o’n ni, nhw = o’n nhw BUT oedd doesn’t have a shortening for third person singular (o/e/hi)
wnes i is another form of past tense used instead of oeddwn i / o’n i when talking of a completed action in the past as opposed to a continuous action in the past
e.g. wnes i gerdded = I walked
mi oeddwn i’n cerdded / roeddwn i’n cerdded / o’n i’n cerdded = I was walking
Thank you. This is very helpful!