Is there one? Can someone explain it? Gura míle!

I think it has something to do with relative clauses. I would also like to know the answer to your question.

I started drafting an answer, and gave up.

There are too many yes, buts involved, since both forms cover a number of different but related cases.

It's a case where I would know which was correct, but couldn't tell you why!

I found this at Foclóir Beag, http://www.csis.ul.ie/scripts/focweb/Exe/focloir.exe

ab [aimsir chaite, foirm choibhneasta dhearfach dhíreach][modh coinníollach, foirm choibhneasta dhearfach dhíreach]

ba [aimsir chaite, foirm dhíreach dhearfach][modh coinníollach, foirm dhearfach dhíreach][aimsir chaite, foirm choibhneasta dhearfach dhíreach][modh coinníollach, foirm choibhneasta dhearfach dhíreach]

Exactly!

There are so many of them. I was hoping one of the grammar geeks would step up to the plate.

In Standard Irish there's the independent, absolute form ba and the direct relative form ab.
And there's no relative clause in X ba ea Y (lit. "X, it is Y") So only ba ea should be expected.

Graiméar Gaeilge na mBráithre Críostaí:
"14.62 Níl ach dhá fhoirm shimplí ag an gcopail (is é sin, dhá fhoirm nach bhfuil aon
fheidhm eile acu ach feidhm briathair)
- is, foirm na n-aimsirí príomha: is bó mhaith í;is amhlaidh atá
- ba, foirm na n-aimsirí stairiúla: cat ba ea é; ba lách an duine é"

But in Munster X ab ea Y is used throughout.

Lars

quote:

But in Munster X ab ea Y is used throughout.

Except for An Rinn: X badh ea Y is used there (badh /bəj/ old form of ba)

Lars

Nach mbaineann ab leis an chlásal choibhneasta amháin (gutaí agus f)
An bhean ab fhiú a mharú
an duine ab fhearr sa rang
(is féidir ba a úsáid anseo chomh maith)
An bhean ba chineálta ar domhan

Ach ní leis chlásal choibhneasta amháin a bhaineann ba, nó tig a úsáid in aon ráitéas deimhneach, chomh maith:
Is carr mór é
Is mór an carr é.
Ach san aimsir chaite:
Ba charr mór é.
Ba mhór an carr é.

Ar ndóigh is le tuilleadh treise a chur ar fhocal a úsáidtear ba ea (is ea) chomh maith,
Is buachaill é.
ach
Buachaill is ea é / Buachaill atá ann
Ba bhuachaill é.
ach
Buachaill ba ea é / Buachaill a bhí ann.

Does ba ea exist?

quote:

Does ba ea exist?

'Sea, sílim.

From Gramadach Na Gaeilge, pg 81,

Coinnitear foirmeacha na copaile scartha ón bhfocal ina ndiaidh, e.g. is é, is í, is iad, is ea (nó sea); ba é, ba í, ba iad, ba ea; srl.

When "ba" hits another vowel, it becomes "ab", as in:

Agus mé ar scoil, ba mé an buachaill ab óige i mo rangsa.
Séamas ab ainm dó.


There's only two cases in which it doesn't become "ab":

1) When it's the first word in a clause:

B'aoibhinn an lá é.
B'álainn an cailín í.
(You'd still use /b'/ in the following: Inné b'álainn an lá é)

2) Past tense for using adjectives to compare stuff:

Bhí do leabharsa ní b'fhearr ná mo leabharsa.
Bhí an cailín sin ní b'áille ná mo dheirfiúr.