Why is „Tá siúl orainn“ wrong? You use this word order with other phrases like „Tá brón orainn“ or „Tá áthas orainn“.
brón and áthas are nouns, siúl is a verb.
As a general rule, a verb can't be a subject of another verb.
Hmm, I will try to wrap my head around it.
How do you know that this means specifically 'we' when there is no conjugation?
One of the ways to express "must" or "have" in Irish is to use Tá ar, where the pronoun is declined for the English subject. So you know it's "we" because it's orainn, which is ar muid.
Caithimid should be acceptable too
'Caithfimid' should be acceptable, but not 'caithimid'. 'Caith' is used in the future - and, occasionally, the conditional - to mean 'must'.
I don't get what "orainn" is
It’s basically the equivalent of the English prepositional phrase “on us”. The way I remember it to mean “we must” for this exercise is to restate it as “it is ON US to walk”.
(Sorry for the caps - I can’t do italics on this device.)
Is there a way of using 'gá' here?
Why siúl not siúlann?
Like in other languages, you can only have one predicate in a sentence and there is already one, namely orainn.
The actual present tense verb in this sentence is tá. The action that you "must" or "have to" do is expressed using the verbal noun. That is more obvious in an example like "we must go to the library" - Tá orainn dul go dtí an leabharlann.