i stem

[john abshire]

Civis, civis, civi, civem, cive
Cives, civium, civibus, cives, civibus

This may be a silly question, but I am asking it to see if I am missing something, and because I have not seen an explanation for why i-stem nouns and adjectives have that name. If you look at how civis, civis declines, you can see the stem is civ, not civi. Other i-stem nouns and adjectives are similar. Is the reason that civis, civis (and others) are called an i-stem noun (or adjective) because most all of the case’s endings contain an i? (and not because the stem ends in an i)?
{I am reviewing 3rd declension adjectives and could not find the answer.}

 

[MIB]

I believe it's because the genitive plural ends in -ium, rather than -um

 

[Matthaeus]

There are exceptions, though. I've seen things like canum for canium.

 

[Pacifica]

I believe the i was originally part of the stem, but it disappeared in some places due to the influence of other third-declension nouns.

 

[Pacifica]

Civis, civis, civi, civem, cive
Cives, civium, civibus, cives, civibus

By the way, there are alternative ablative singular and accusative plural forms where the i is still there: cīvī (abl. sg.) and cīvīs (acc. pl.).

Such variants exist in many i-stem nouns. Some even have an accusative singular in -im, but that's much rarer (only a handful of nouns have that—e.g. navim, puppim, turrim; civis isn't one of them).

 

[Hector]

The word "stem" is used in multiple ways. Defining the "stem" as the part of a word that's shared between all case forms is pedagogically convenient, but there are other definitions of "stem". From an etymological perspective, or a more generalized analysis of Latin, rather than saying that there are different nominative singular endings -us, -s, -is, -us, -es for different declensions of nouns, we can identify a shared nominative ending -s found at the end of all of dominus, rex, civis, actus, dies. The part before the -s in the nominative form is therefore part of the (original or abstract) stem of the word, not part of an inflectional ending: e.g. the stem in this sense of dominus is domino- (the original o was turned to u by sound change).

Aside from sound changes that modify the final sound of a stem, making it look like that sound is not part of the stem, some words are genuinely built on multiple stems (e.g. the nominative senex vs. the accusative senem). Words with multiple stems are called "heteroclite". Third declension "mixed" i-stems (which outnumber "pure" i-stems) can be analyzed as heteroclite (having an i-final stem in forms like the nominative singular in -is and genitive plural in -ium, and a consonant-final stem in forms like the accusative singular in -em), although in some cases the forms without /i/ may have developed phonetically from forms with original i/y (e.g. if I remember correctly the nominative plural ending in -es comes from earlier -eyes with elision of intervocalic y).