I know I'm either opening a can of worms or asking a basic question---indulge me, please.

Can anyone explain how/why Ar versus An fits into these verb conjugations. I know Ar as "on" or "our" and An as "the"--I'm obviously missing something.

Ar ith tú? An bhfaca tú? An raibh tú?

Go raibh mile maith agaibh, in advance.

Le meas,

James

James, a chara,

The question is good. It pertains to irregularity of the verb versus regularity. Some irregulars are more irregular than others!

The basic pattern is 'an' being used with your ordinary question, present tense and 'ar' being used with the past. Irregular verbs, some, not all, refrain from such simplicity and continue to take 'an' in the past tense questions. Some Gaeltacht areas are less prepared to adapt to 'ar' with some of the irregulars in the past tense, so one can hear both 'an dtáinig ...?' as well as 'ar tháinig ...?' in modern speech.
Some areas have gone the other way and 'regularized', so to speak, a bit too much, hence
'ar chuaigh ...?' as against
'an ndeachaigh ...?' or even
'an dteachaidh ...? which also developed.

Ná cuireadh a dhath beo ná marbh aon iontas ort agus má fheiceann tú ceann na muice ar an mart, ná haithris é!
Be prepared to accept anything as it comes!

Tiocfaidh na foirmeacha seo in aithne duit le himeacht ama agus le himeacht na léitheoireachta go háirithe.

Go n-éirí go seoigh leat ar thuras na fionnachtana!

James, a chara,

Just one other thing that may help: You will probably have a better time of it if you think of "ar" meaning "on" and "ar" being used to form a question in the past tense, as two different words altogether. ("ár" meaning "our" should normally have a fada, and will sound different.) Similarly, and indeed particularly with "an" meaning "the" and "an" used to form questions in the present, future and conditional tenses - I say particularly because the two do not behave the same way grammatically.
When being used to form questions, "ar" and "an" are known as "interrogative participles" (I think!) and are not directly translateable into English. Just think of them as meaning "?"!!
The only similar type example I can think of off hand in English is something like the word "record":
I bought a record yesterday.
I record films off the telly every week.

Although they look they same, they are in fact two different words. In other words, these are meanings you will pick up from the context of the conversation.

When you think about it, English can be just as baffling: if you think of trying to explain the word "do" in a normal sentence like "Do you go to the cinema often?" instead of the more gramatically straightforward but rather archaic(!) "Go you...?". There's no easy way to explain it except to say "don't think about it too deeply, just accept that that's the way it's done".

Hope that's helpful,
Mise le meas,
Nicole

Ar agus Níor agus Gur agus Nár
------------------------------

Used in the past tense only.

Ar rith tú?
Níor ghlac mé.
Dúirt sé gur thóg sé.
Dúirt sé nár thóg sé.

An agus Ní agus Go agus Nach
----------------------------

Used in every single other tense

-

There's 6 and only 6 exceptions to the above. They're all in the past tense. It's just pure irregularity:

Chuaigh -> Ní dheachaigh, An ndeachaigh, go ndeachaigh, nach ndeachaigh

Chonaic -> Ní fhaca, An bhfaca, go bhfaca, nach bhfaca

Dúirt -> Ní *dúirt, An ndúirt, go ndúirt, nach ndúirt

Fuair -> Ní *bhfuair, An bhfuair, go bhfuair, nach bhfuair

Rinne -> Ní dhearna, An ndearna, go ndearna, nach ndearna

Bhí -> Ní raibh, An raibh, go raibh, nach raibh

* = not an error

-Phil

http://homepage.eircom.net/~kuichinneide/reimircaite.html

Try this link, it might throw some more light on the subject.