Morphological criterion

The singular form criterion is used in the heading because what is at stake is simply whether a given word allows grammatical suffixes or not. This criterion is the least important of the four listed above and is more relevant to some languages than others. It is of the greatest interest with respect to languages such as Russian, in which nouns have different suffixes (‘endings’ in the traditional, informal terminology) depending on their relationship to the verb. Examples are given in (1).

The noun sobaka in (1a) splits into the stem sobak- and the suffix -a, which here signals the animal doing the barking. In (1b), sobak- has its direct object suffix -u, which here marks the animal being scratched; in (1c), it has its oblique object suffix -e, which here marks the recipient of the bone. A few nouns in Russian take no suffixes, for example taksi (taxi), kofe (coffee) and kakadu (cockatoo). (Such nouns do not vary their shape and are called invariable words.) English does not have the same range of grammatical suffixes as Russian, but English nouns typically take a plural ending – fish–fishes, cat–cats and dog–dogs. (The -srepresents different suffixes in speech – in cats it represents the initial sound of speed, in dogs the initial sound of zap.) Some nouns in English do not take a plural suffix – for example sheep, deer – and are said to be invariable.