Translation:Blianta, míonna, seachtainí, laethanta agus uaireanta.
Well if that doesn't express the seemingly randomness of irish plurality then i just don't know what does
Why is it uaireanta intead of uaireanna? Uaireanta is sometimes, uaireanna is hours?
laethanta ... are there really broad and slender vowels around the 'th'? How can it be!?
ae is treated as a single broad "digraph".
It is fairly rare, but apart from laethanta, the other common example is Gaeltacht.
Aeráid, traenálaí and aerfort are some of the ordinary, but slightly less common, words containing this broad digraph that you will encounter in exercises on Duolingo.
(This isn't considered an exception to leathan le leathan, caol le caol, as ae is always considered leathan).