Watam has two major word classes: noun and verb, each distinguished by their paradigms of inflection. In addition to these, there are 7 minor categories: adjective, quantifier, locational, temporal, pronoun, deictic, and interjection. There is a smallish set of true adjectives, which are distinguished by the fact that they agree in number with the nouns they modify, a feature true verbs lack. Quantifiers are distinguished from adjectives in that they lack number agreement with the nouns they modify. Locationals and temporals are two adverbial-like parts of speech expressing the spatial and temporal orientation of events and participants. Some of these share features of both the nouns and verbs, such as their ability to pluralize or be inflected for tense-aspect.
The number distinctions of Watam pronouns, like those of Yimas, is richer than many Papuan languages: in addition to the usual three persons, four numbers are distinguished: singular, dual, paucal (a few) and plural (more than a few). Deictics, on the other hand, are greatly unelaborated. There is only one true deictic form, the PROXimal deictic an 'this': markum an 'this pig'. There is no true distal deictic form, i.e. 'that'. The third person singular pronoun ma 'he/she/it' can be used as an anaphoric deictic much like English 'that': ma markum 3SG pig 'that's a pig', but never in combination with a noun in a noun phrase: *markum ma 'that pig'. Finally, like many Papuan languages Watam lacks true conjunctions, their function being filled by suffixes to dependent verb forms.