In chapter 1 of "Teach yourself Irish", we learn about the genitive singular and normative plural forms of nouns. Why hold back the normative singular and genitive plural? To me (a huge noob at Irish/grammar/languages) it seems a bit arbitrary...

Is the reason we first introduce the nominative plural and genitive singular together because these forms just happen to be very similar quite often? And so as long as we are learning one, we may as well learn the other?

I hope this doesn't come off like another "meta-learning" post that I so oft make around here... I'm legitimately asking this question with the hopes it can bring clarity to my studies.

In the 1st declension, which is introduced in that chapter, the nouns are masculine. The nominative singular and genitive plural are identical. The genitive singular and nominative plural are identical (and have a slenderised ending)


The word: an focal
Of the word: an fhocail (brí an fhocail - the meaning of the word)
The words: na focail
Of the words: na bhfocal (bríthe na bhfocal - the meanings of the words)

The priest: an sagart
Of the priest: an tsagairt (tigh an tsagairt - the priest's house)
The priests: na sagairt
Of the priests: na sagart (tithe na sagart - the priests' houses)