
Cameron B. answered 07/28/21
M.A. with two years of Graduate Latin & Three Years of teaching
First, the connecting vowels of these declensions reflect the Gender of word. For instance, -o/u/e tends to be Masculine or Neuter, but -a tends to be Feminine. There are exceptions, such as the Neuter Nom./Acc. Plural which ends in -a. The reason for this is because the feminine 'alpha' (left over from Greek/Proto-Indo-European languages) was fundamentally used to speak of collective units. Thus, the unusual case of Masculine First Declension Nouns ending in -a is found most in nouns stating an occupation such as nauta (masc.) meaning "sailor." Below is a detailed chart showing similarities as well as differences between the declensions:
1st & 2nd Declension
Gen. Pl.: -ōrum/-ārum [Contrast: Only difference is between the connecting vowels -ō/-ā which reflect the change in gender; -ō is Masculine & Neuter; -ā is Feminine]
Acc. Sing.: -um/-am [Contrast: similarity is the -m suffix attached to the connecting vowel. The connecting vowels reflect the change in Gender; -um is Masculine or Neuter; -am is Feminine]
Acc. Pl.: -ōs/-a/-ās [Connecting vowel is different between Masculine and Feminine with the similarity being with the -s suffix. The exception here is Neuter Accusative Plural is different from the masculine -os, being -a, not to be confused with 1st Declension Nom. Sing. See above for explanation of this.]
Abl. Sing.: -ō/-ā [Connecting vowel is different between Masculine & Neuter/Feminine]
Hope this helps!
~Cameron Brock