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I reported it as an error, but I'm not sure that I'm right. Is this an exception to the DNTLS rule?
It is an error, but in this case it’s more of a “DTS” rule: an doesn’t lenite a singular feminine noun’s initial consonant if that consonant is either D, T, or S.
Can someone do a quick rundown of the dentals and dots rules?
In places where lenition would normally occur, it does NOT happen to nouns beginning to D, T, or S when they follow words enting in D, N, T, L, or S.
OK. Does it have the same effect on eclipsis as well?
Eclipsis is a little bit different. D and T are not eclipsed where they ordinarily would be after the article "an," but they ARE eclipsed after the interrogative particle "an."
Ta se ag an doras (not "ag an ndoras")
An dtuigeann tu?
GRMMA, I think I have that now. The interrogative particle is the exception.