thanks I should have realised. I was not thinking literally; what does ta actually mean?
Why "ball" and not "sphere"? The first time I encountered the word, the translation given was "sphere."
The Irish for the geometrical shape of a ball is sféar.
You could stop 100 people walking down any street in Ireland, and ask the people who did Irish in school what liathróid means, and every single one of them would say "ball", and I doubt that many of them could tell you what the Irish for "sphere" is (I had to look it up to answer your question!
GRMA duolingo, you just reminded to put an new exercise ball on my shopping list.
I'd try to write this in irish but dont know "reminded" or exercise!
Why is "ciseán" lenited here? I was under the impression that preposition + "an" → eclipsis.
There isn't a single rule that applies to all prepositions. Some lenite the following noun, some eclipse, some done cause any change, some eclipse after an, some lenites after an.
sa lenites a following noun, but it also follows the DNTLS DTS exceptions, because sa used to be ins an.