Nouns generally refer to objects, places, events, groups of things, or ideas. They can function as subjects, direct objects, indirect objects, instruments, as the objects of prepositions, or even stand outside the sentence proper in direct address. In Çomyopregi nouns decline to reflect two categories. One of these is number (singular or plural). The other is case. Çomyopregi nouns do not have gender, so you will not have to think about the masculine, feminine, and neuter as in French, German, and so many other European languages. They're asexual. Fortunately, the case system more than compensates for the simplicity in that aspect. Nouns decline, altering their endings to reflect both number (singular or plural) and case (representing their function in a sentence). There are six cases: nominative, genitive, dative, accusative, instrumental, and locative. The singular forms of domu, "house", for each of these cases are:
The nominative singular is also the citation form, the form given in dictionaries. All nouns which have a nominative singular in -u are declined like domu. There are other patterns of declension, depending on the different endings of the nominative singular, which can be -a, -o, -i, -u, -r, or -n.
The different noun stems are divided into four groups: Class I nouns (thematic stems) end in -a and -o; Class II nouns end in -i and -u; Class III nouns end in -r or -n (here the stem vowel is whatever vowel appears before -r or -n); Class IV also ends in -o in the nominative singular, but in most other forms has a suffix -es, and this suffix is considered the stem, not the -o of the nominative.
| "moon" | "wolf" | "sea" | "eye" | "house" | "father" | "holly" | "name" | "word" | |
| Nom | luna | ulquo | mori | oqui | domu | patir | caghón | noma | uiquo |
| Gen | lunasyo | ulquosyo | moryos | oqueyos | domuis | patros | caghonos | nominos | uiquesos |
| Dat | lunáy | ulquóy | morí | oquí | domuy | patrí | caghoní | nominí | uiquesí |
| Acc | lunam | ulquom | morim | oquim | domum | patira | caghóna | nomina | uiquesa |
| Ins | luná lunavé |
ulquó ulquové |
moryé | oqueyé | domué | patré | caghoné | nominé | uiquesé |
| Loc | lunay | ulquoy | morí | oquí | domui | patri | caghoni | nomini | uiquesi |
| Nom | lunás | ulquós | morís | oquís | domús | patires | caghónes | nominis | uiquesis |
| Gen | lunavom, lunám |
ulquovom, ulquóm |
moryom | oqueyom | domuim | patrom | caghonom | nominom | uiquesom |
| Dat | lunavyo | ulquovyo | morivyo | oquivyo | domuvyo | patirvyo | caghombyo | nomimbyo | uiquefyo |
| Acc | lunan | ulquon | morin | oquin | domun | patiras | caghónas | nominas | uiquesas |
| Ins | lunavi | ulquovi | morivi | oquivi | domuvi | patirvi | caghombi | nomimbi | uiquefi |
| Loc | lunachu | ulquochu | morichu | oquichu | domuchu | patirru | caghonsu | nominsu | uiquessu |
Note, all nouns in -ui or -yi follow the pattern of oqui instead of mori, having -ey- in the genitive and instrumental singular, and genitive plural. Also, the exact pattern of declension for n- and r-stems varies, because each has multiple stems, which do not always coincide — one for the nominative and accusative (singular and plural), and another for the other cases (in addition, they all form the dative and instrumental plural uniformly, as indicated in the table). Finally, the nominative singular of s-stems is the same as that of o-stems, and the nominative singular of some n-stems (noma) is the same as a-stems. In general, you should know at least the nominative and genitive singular of any noun you wish to decline. The genitive singular is often given in parentheses in dictionaries.
Each of the cases has particular functions unique to it. Often, these may be equivalent to the use of certain prepositions in English. The basic uses of each of the cases are as follows: