4.1. Declension of Nouns

4.1.1. Declension is made by adding terminations to different stem endings, vowel or consonant. The various phonetic changes in the language have given rise to the several declensions. Most of the case-endings, as given in Indo-European, contain also the final letter of the stem.

Adjectives are, in general, declined like nouns, and are etymologically to be classed with them; but they have some peculiarities of inflection.

4.1.2. Nouns are inflected in four Declensions, distinguished by the final phonemes, characteristic of the Stem, and by the opposition of different forms in irregular nouns.


Stem ending




 -i, -u, -i, -u and Diphthongs

-s, -Ø

-e/ois, ios ; -e/ous, -uos


Sonants and Consonants

-s, -Ø

-e/os, -s


-a, -ia /-i / -ia, -e, -o




-e/o (thematic)


-os, -osio, -oso, -i


Variable Nouns



The Stem of a noun may be found, if a consonant stem, by omitting the case-ending; if a vowel stem, by substituting for the case-ending the characteristic vowel.

4.1.3. The following are General Rules of Declension:

a. The Nominative singular for animates ends in -s when the stem endings are -i, i, u, u, diphthong, occlusive and thematic (-os), or -Ø in -a, -a, sonant and -s; while in the plural -es is general, -s for those in -a, and -os for the thematic ones.

b. The Accusative singular of all masculines and feminines ends in -m; the Accusative plural in -ms.

c. The Vocative singular for animates is always -Ø, and in the plural it is identical to the Nominative.

d. The Genitive singular is common to animates and inanimates, it is formed with -s: -s, -es, -os. A very old possibility is -osio. The Genitive plural is formed in -om and -em, and also in -am in a-stems.

e. The Obliques singular end usually in -i: it can be -i, -ei, -ei, -oi, -oi or -ai. In the plural, there are two series of declensions, with -bh (general) and -m (only ger. and sla.), generally -bhi, -bhis, -bhios, -mis, -mos, and also some forms in -si (plural mark -s- plus oblique mark -i), mainly in the southern dialects.

f.  Inanimates have a syncretic form for N.-Ac.-V. in -Ø in athematic, or -m in thematic. The plural forms end in -a or -a.

g. All Animates have the same form in the plural for Nom.-Voc., in -es.

4.1.4. The Oblique cases, opposed to the Straight cases (Nom.-Acc.-Voc)  are Genitive and the Oblique cases, i.e. Dative, Locative, Instrumental and even Ablative. However, the Ablative was never independent, but for thematic stems in some dialectal areas. The other three cases were usually one local case in different contexts, although there are sometimes different declensions for groups or even for the three of them.

NOTE 1. There some traces (in the IE proto-languages which show divided Oblique cases) that could indicate a possible first division between Dat. and Loc.-Ins., and then another, more recent between Loc. and Ins.

NOTE 2. What we know with certainty is that the splitting and merging processes that affected the Obliques didn't happen uniformly among the different stems, and it didn't happen at the same time in plural and singular.

NOTE 3. Before we begin with declensions, it is necessary to point out that there was neither a homogene and definite declension system in IE III, nor in the dialects and languages that followed. From language to language, from stem to stem, differences over the number of cases and its formation developed. Firstly syncretism obscured the cases, and thereafter the entire system collapsed: after the time when cases broke up in others, as in most modern Slavic languages, another time came when all cases merged or were completely lost: so today in Romance languages, in Germanic like English, or in the Slavic Bulgarian,... It is necessary, though, as with Europaio, to systematize to some extent this diversity, based on the obvious underlying old system.