1. The following table depicts the general system, common to the First and Second Declension.
| 
 
  | 
 Animate  | 
 Inanimate  | 
| 
 NOM.  | 
 -es  | 
 -a, -a  | 
| 
 ACC.  | 
 -ms  | 
|
| 
 VOC.  | 
 -es  | 
|
| 
 GEN.  | 
 -om, -em  | 
|
| 
 OBL.  | 
 -bhis, -bhos; -mis, -mos; -si  | 
|
NOTE. The inanimate plural forms, -a and -a, correspond possibly to an older theme vowel of an earlier stage of the language, *-h and *-eh after the Laryngeals' Theory.
2. Unlike in the Singular, in which only some Nominatives have an -s, in Nom.-Voc. Plural the -s is general, and there is always one fix-grade vowel, e. So, the opposition Singular-Plural in -s/-es is actually a Ø/e distinction. This opposition has also sometimes another mark, that of the vowel before the ending (see § 4.7).
3. The Nom.-Voc. Plural Animate is normally in -es; as in cowes
There are forms in -eies for -i themes, as in oweies; in -eues for -u themes, as in suneues; in ijes, -uwes for -i, -u; as in bhruwes;
4. The Accusative Plural Animate is in -ms: owims, sunums, coms/coums
NOTE. Many scholars reconstruct for IE III the accusative plural ending -ns, because most of the attested proto-languages show either -ns (as some endings in Sanskrit or Germanic) or long vowel, sometimes with -s. Most of them also admit an original, older -ms form (a logical accusative singular -m plus the plural mark -s), but they prefer to reconstruct the attested -ns, thus (implicitly) suggesting an intermediate phase (IE II -ms> IE III *-ns> proto-languages -ns/-_s), common to all proto-languages. We don't know if this intermediate phase happened, and if it was common to all languages, or even if it was common to those languages which present in some declensions -ns, and in other declensions another endings. What we do know is that the form -ms is older than any other, and that it existed already in the IE II dialects, as the Anatolian shows.
5. Nom.-Voc. Acc. Plural Inanimate in -a
6. Genitive Plural Animate in -om/-om and -em: owi-om, noqti-om, sunuw-em/sunuw-om, cow-om
NOTE. The -m of the Acc. sg. An., Nom.-Acc.-Voc. sg. Inan. and this case could sometimes be equivocal. It is disambiguated with the vocalic grade, full or lengthened, which the Genitive takes - as the singular is always Ø.
7. The Obliques are generally divided into two groups, that of the i.-i., gr., arm., lat., and cel. in -bh-; and another of the ger. and bsl. in -m-. There are, thus, -bhis, -bhos, -bhios, -bhi, and -mis, -mos: sunubhis / sunubhos / sunubhios / sunumis / sunumos.
There is also another possible ending, mostly (southern) dialectal, in -si: sunusi
NOTE. This has probably an origin in the plural mark -s-, to which the local case ending -i is added. This is a general oblique ending in the thematic declension.
| 
 
  | 
 f. owi  | 
 m. sunu  | 
 f. bhru  | 
 m. cou  | 
| 
 NOM.  | 
 oweies  | 
 suneues  | 
 bhruwes  | 
 cowes  | 
| 
 ACC.  | 
 owims  | 
 sunums  | 
 bhrums  | 
 coums  | 
| 
 VOC.  | 
 oweies  | 
 suneues  | 
 bhruwes  | 
 cowes  | 
| 
 GEN.  | 
 owiom  | 
 sunuwem  | 
 bhruwom  | 
 cowom  | 
| 
 OBL.  | 
 owebhos  | 
 sunubhis  | 
 bhrumis  | 
 coumos  |