Fòram na Gàidhlig

Tha mi ag ionnsachadh leis Beag air Bheag.
Aonad 5, Transcript 1
Can Iaian 'Am fosgail mi an uinneag?'
Can Eilidh 'Fosglaidh', ... 'Fosgail an uinneag'
Carson 'fosglaidh'?
Agus 'Dà seòmraichean', ach 'Cia mheud seòmar ... ?'
Carson an cumadh singilte?
Bidh mi tangeil do gin cuideachadh.
Gin ceartachadh fàilte.

I am learning with Little by Little.
Unit 5, Transcript 1
John says 'Shall I open the window?'
Eilidh says 'Close it', ... but then uses a different word.
Why 'fosglaidh'?
And 'Two rooms', but 'How many room?'
Why the singular form?
I will be grateful for any help.
Any corrections welcome.

Gaelic has no words for "yes" and "no", so what you do is repeat the verb in the question in its positive/negative form: Am fosgail...? - Fosglaidh!/- Chan fhosgail!

Both "dà" and "Cia mheud" are followed by the singular. The reason is historical: dà used to have a special dual form, and we still see some vestiges of it (the lenition, and in formal speech, feminine words will also be slenderised). Cia mheud: meud is a noun, and the last noun in a string of nouns is always put in the genitive case. Since historically the genitive plural looked a lot like the basic singular form, it got replaced by the singular here. Same for big number words like fichead, which are also followed by the singular. Confused yet?

Tapadh leat a-righist, a GhunChleoc. Tha thu glè carthannach. Bha an ceist leis 'fosglaidh' -- carson cha 'fosgail'? Tha an mineachadh gu dà agus cia glè inntinneach.

bodach wrote: Bha an ceist leis 'fosglaidh' -- carson cha 'fosgail'?

Because the person is answering the question. "Fosglaidh" is positive future open, so "yes" in his instance. "Fosgail" on its own would be an order, not an answer.

Gaelic is a "dependent-marking" language, this means that the form of the verb depends on what come before it.

I (will) open - Fosglaidh mi

Will / do I open...? - Am fosgail mi...?
Won't / Don't I open....? - Nach fosgail mi...?

Yes - Fosglaidh (as an answer to these questions)
No - Chan fhosgail (as an answer to these questions)

Tapadh leigh a Ghuncleoch agus a Nìall Beag.