noun stems

[lonsdale]

I am confused about noun stems.

I've checked in a couple of textbooks, some online sources, and an article on this website, and I still don't understand.

First declension nouns have stems in "a"? I don't get that. "a" endings, okay, but I don't see an "a" in the stem of puella.

Second declension with stems in "o"? As in "colonus"? What about ager and puer?

Third in consonants? I think I get that. "Rex" ends in a consonant.

Am I just missing the point?

I would love to understand.

[modus.irrealis]

Well, historically speaking, first declensions did have a stem in a and second declensions a stem in o, but that got obscured and the final stem vowel and the endings merged so it's hard to see that. People compare Latin with Greek and other Indo-European languages and you can see that in colonus, the original o has become u, in ager (compare Greek agros), the o has just been dropped. So the nominative colonus is stem colono- + ending -s, just like rex is stem reg- + ending -s.

My experience is that some books, especially older ones, take this historical approach, but others will say that the stem of puella is puell- and -a is the ending. I find the latter analysis easier for learning, but the former is important too if you become interested in the history of the language and its connections with other languages.