Poswa nouns

Poswa preserves the six noun cases of the parent language with almost no changes in meaning or form, apart from regular sound changes. The possessive has weakened into a genitive when used with definite nouns, however. e.g. teppiopwas mupawabub "the length of the rope". Poswa has not added any new cases; so there is still no dative case and the various uses of the locative case are not distinguished.

• Nominative: The default form of the word, used as the subject of a sentence and also in genitive phrases when not indicating possession; paslam "fire"; paslam boša "fire hearth; fireplace".
• Accusative: Always marked by -p, shows the object of a verb. Žazba pasliap blabwambi "The girl put out the fire".

Number and animacy

Poswa distinguishes between animate and inanimate nouns, but there is no grammatical marker distinguishing the two; they simply must be learned. However, in nearly all cases, the difference follows semantics, so this is not a source of difficulty for students of Poswa.

Plural suffixes

There is no "grammatical" plural in Poswa in the sense that there is not a separate table of forms for plural nouns in each declension. To pluralize a noun, either -by or -bum is added. The difference between the two is that -by implies separation amongst the individual items being described, whereas -bum implies that they are working together. An animate noun can take either of the two suffixes depending on which meaning is intended; inanimate nouns have a fixed plural form, however, in a manner similar to the way nouns have genders in Spanish and some IE languages. Learning the pattern here is much more difficult than learning the difference between animate and inanimate nouns because there is no significant connection between the semantic meaning of a noun and the categorization of that noun as belonging to the -by or the -bum class. Such words are simply called "by nouns" (blwaššum) and "bum nouns" (bumblaššum) in Poswa.

The -by and -bum suffixes interact with the nouns they modify, particularly those ending in voiceless consonants, using the same sound rules that other compounds do. For example, the noun paspys "square" pluralizes to paspyžbum because of a sound rule automatically changing all sb to žb. Poppup "knife" changes to poppubum because of a sound rule automatically changing all pb to bb and another one causing the simplification of the second of two consecutive geminate consonants. The -by suffix merges in different ways.

Loanwords are generally placed into the bum class, making it the more productive of the two. A small number of native words have changed class over time, often due to reanalysis. For example, the native word for "rain" was pleb, a regular development from Babakiam piyu. But this came to be seen as a plural consisting of a dummy stem ple and the plural suffix -by (the final y is usually ommitted in Romanization, as there are no words with a plain final -b.) Thus a new word, ple, meaning "raindrop" was coined, which has no Bābākiam form. Then, a new plural plebum came to be used for the more common noun "rain", and pleb fell out of use. A similar story explains what happened to the commonest word for an army. Originally, the word for army was pamby, a regular development from Bābākiam pamimiu. This was a singular noun. However, it came to be reanalyzed as a plural, and given that the -by suffix generally denoted things that were seen as separate pieces, not part of a greater whole, the word was changed to pambum to reflect a unified army. Note that this new word has no singular form, and that "double plural" forms such as *pambumbum used to mean "armies (plural)" are considered inappropriate. Instead the pambum word is used with a modifier meaning "several", "many", or whichever meaning is intended.

Singulatives

From nouns that denote crowds or mass nouns, a singulative suffix -ba can be added to denote one piece or one member of it. For example blub means "milk", and blurba (due to a sound rule) means "a bit of milk; some milk (to drink)". Note that this -ba suffix is derived from Bābākiam viba, not ba, and therefore does not collapse the way some other suffixes beginning with -b do; the /b/ remains always a /b/.

Animacy

Note that body parts, and inalienable nouns in general, inherit their animacy from an implicit "parent noun", and therefore are understood as animate nouns in any context, even if the person whose body they belong to is a corpse or a doll.

In a very old stage of the language, an infix -a could be inserted into any inanimate noun to make it an animate one. A few doublets still survive, but this infix was never used often and few speakers are aware of its former existence.

Possession

Possession markers can be placed on any noun, e.g. papwopwa "dog"; papwopio "my dog"; poppup "knife" ---> poppuwio "my knife". The stem to which the possession marker attaches is called a soppu.

Noun declensions

Noun declensions are complicated by the fact that unlike Poswa verbs, Poswa nouns change even the stem when an inflectional suffix is added. That is, there is no "barrier" between the stem and the suffix that keeps the stem mostly intact. Instead of declensional tables, the entire last syllable must be taken into account in order to determine the various forms. Thus it could be said that there is a declension for every syllable. However, with just a few simple rules, the patterns can be easily perceived.