I just started learning Swedish and I noticed that the neuter plural forms of adjectives (I assume also nouns) usually have the same endings as the singular "common" (a merging of feminine and masculine) adjectives. In Latin, there's the same pattern with -a and -ae feminine endings and -um and -a neuter. In Greek, the same thing exists with feminine nouns and adjectives ending in -a (some others end in -i, though). Also, it basically seems that all neuter forms have a singular that looks like the masculine and a plural that is the same as the feminine singular. In PIE was there some similarity between the forms that made this happen? And where exactly did the neuter even come from? Was it just some sort of merge as it would appear to be?