So I finished "Prepositions after Verbs" in Ó Nualláin's Studies in Modern Irish (the chapter on prepositions).

Some listed verbs have -(a)im endings, e.g. maoidhim, tigim, tagaim, seasaim... There's also toilighim. Yet other verbs are listed like teastuigh, labhair, etc. without these endings.

I did some digging, and I believe that the aforementioned maoidhim, tigim, tagaim, etc. are the first person imperative (seems identical to the singular first person present indicative).

Ó Nualláin lists sgar (scar), scaoil, etc. in other instances, which seem to be the second person imperative.

Why are some verbs listed in the first person, and others in the second person imperative here? Leads me to wonder what the correct convention is when just listing verbs like that. I believe it's the second person imperative in dictionaries today, but here there's both that and the first person imperative. Ó Nualláin is also Ó Nualláin, so there's probably a good reason I'm missing.

GRMA.

There is no single “correct” convention, but typically dictionaries will now opt for 2nd person singular imperative, with 1st person singular present tense being a somewhat outdated alternative. If you look at headwords for verbs in Ó Dónaill, for example, they will be listed under the 2nd person imperative form (see examples: gabh, faigh). Still, when you look up the same verbs in de Bhaldraithe, you’ll see that that dictionary uses 1st singular present forms instead (see examples: tógaim/gabhaim, faighim).