"I need an ambulance, please."
Translation:Tá otharcharr uaim, le do thoil.
I have formed the impression that "tá ,,, uaim" means "I want" or even "I need", and that "teastaíonn ... uaim" means emphatically "I need".
So why is "teastaíonn otharcharr uaim le do thoil" wrong?
Teastaíonn otharcharr uaim le do thoil should be perfectly acceptable.
As to the meaning, the form of bí ó can only mean 'want'. It got accepted as 'need' because of a non-literal translation, which is some dialects (my own included) would still have used 'want'.
As for teastaigh, it depends. In some dialects, teastaigh can be either 'need' or 'want'. However, in Connemara, it can only be 'need'