Why is sna used instead of sa sometimes for singular things, yet the hint says sna is for plural words. I'm pretty confused about this, not on just this lesson.
sna is not used for singular, only for plural. You'll sometimes see san however, which happens before a vowel sound (so, any vowel, or fh+vowel after lenition, like san fharraige - which would actually be sa bhfarraige in some dialects)
What do you think? the worst day i have had. I think i need to start again at the beginning