Technically, I think there is a direction it just usually doesn’t matter.
Is é an X an Y = The Y is the X
Usually it can be read both ways. However “the X” is always emphasised.
Is mise an dochtúir = (literally) The doctor is me, with me (=mé) emphasised (=mise).
However there is a difference between these two questions:
An é sin an capall dubh?
An é an capall dubh é sin?
Let’s say there is an object in the distance. The first question asks “Is the black horse that object over there?” To which
you could answer “No, it’s the object here”.
An é sin an capall dubh?
Ní hé, Sidé é.
The second question asks “The object in the distance, is it the black horse?”, to which you could answer
“No, it’s the white horse.”
An é an capall dubh é sin?
Ní hé, ach an capall bán.
I don’t know how much the “direction of implication” is maintained today, but older native speakers told me that
this was a distinction.
