Why is it "na léachta" instead of "an léachta"?
tar éis is followed by the genitive. And it's na because léacht is a feminine noun. In genitive singular, only masculine nouns use an.
tar éis is followed by the genitive because it literal;y means, 'beyond a trace'
tar éis na léachta = Beyond the lecture's trace.
What is the singular word for friend?
How would you say 'after the lectures'?