In French you also often say "dans les bois" even when it's in one wood. I guess it's because there are many trees to the word that means the group of trees also is in the plural by analogy.

_________________
Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

I can also confirm 'dans les bois-in the woods' as is said in French or in English, but going on what Bríd says, apparently it would more normal to say it in the singular in Irish. I have however found an example of sna coillte in Pota Focal that comes from Beo - perhaps the writer is being influenced by English, I don't know.
www.beo.ie/alt-seal-in-aotearoa-cuid-8.aspx
it's in the fourth line down below Baile faoi talamh
(by the way in Breton, would you say koad or koadoù ?)

Normally in Breton you say "koed" (I speak Vannetais), and normally "koedaou" is when there are several woods, really several areas with trees. A double plural also exists: koedaouier, but I'm not sure what is the difference between koedaou and koedaouier, if there is any.

_________________
Is fearr Gaeilg na Gaeltaċta ná Gaeilg ar biṫ eile
Agus is í Gaeilg Ġaoṫ Doḃair is binne

I think English used to use the singular "in the wood" for one particular group of trees, but most dialects have shifted to plural "in the woods", possibly through the influence of Teddy Bears' Picnic - "If you go down in the woods today ..."

_________________
Múinteoir Gaeilge - Irish Teacher
My "specialty" is Connemara Irish, particularly Cois Fhairrge dialect, but I can also speak Ulster and Munster Irish with native-level pronunciation.
Is fearr Gaeilge ḃriste ná Béarla cliste, cinnte, aċ i ḃfad níos fearr aríst í Gaeilge ḃinn ḃeo na nGaeltaċtaí.
Gaeilge Chonnacht (GC), go háraid Gaeilge Chois Fhairrge (GCF), Gaeilic Uladh (GU), Gaelainn na Mumhan (GM), agus Gaeilge an Chaighdeáin Oifigiúil (CO).

Teddy Bears - the root of all evil!

_________________

Hahaha. Yeah, I have heard "in the wood" too, Breandán. It doesn't sound incorrect to me but at the same time it does not sound like the natural way of saying it in my part of America. Cool reference, btw. LOL