Fòram na Gàidhlig

Hello, I am trying to figure out how to use the 'S e X a tha ann an Y construction in the past tense. When I looked up is on Am Faclair Beag, I was directed to a Dwelly entry that told me the past tense was bu. However, it seems to me that bu is used in phrases like b' toil leam, 'I would like' (if I'm remembering right). Because of these other usages of bu, is there a better way to say 'She was a librarian' than Bu e leabharlannaiche a tha innte? (That feels incorrect as I'm also unsure of using tha in a past tense construction.)

For clarification about what I mean by 'past tense', I'm writing about someone who is no longer alive but was a librarian her whole life. (In Spanish I know this would call for the imperfect, ie ella era bibliotecaria, but I'm not sure how forms of the past tense in Gaelic are classified as I have only learned the rach --> chaidh sort of past tense so far.)

Mòran taing!

There are two ways:

'S e sgarbh a th' ann >
a) 'S e sgarbh a bh' ann
b) B' e sgarbh a bh' ann

Both are correct but a) is most commonly heard. My interpretation is that b) is perceived as somewhat redundant i.e. in b) you are marking the past tense twice (once in B' and once in bh').

My rule of thumb would be that for everyday use, a) is the best pattern. If you're doing something very formal, go for b).

b' toil leam, 'I would like'

Almost. Bu toil leam, the vowel is dropped before another vowel but not if a consonant follows. That's a general rule for spoken Gaelic which sometimes carries over into written Gaelic.

Bu e leabharlannaiche a tha innte?

There is something a bit like that. It's not everyday speech but you could say Is sgarbh mi which in the past would become Bu sgarbh mi. Normally you don't get that construction except in sayings and some almost fixed phrases involving an adjective:
'S mòr am beud >
Bu mhòr am beud

Hope that helps

Thanks, akerbeltz! I see why option a is more common, as when I think about it literally, it's roughly 'It is a librarian that she was' versus 'It was a librarian that she was', which does sound redundant (the literal literal 'in her' etc nonwithstanding). This is great, as it's something I've always wanted to be able to say but have never known! Thanks again.