Grammatical number is considered to be present in a language if there exists an obligatory grammatical strategy to mark whether nouns, pronouns, or verbal arguments (either explicit or implicit) consist of more than one entity. The number of distinctions available in a number system may vary, with the minimum being a contrast between one (singular) and two or greater (plural). More complex systems may include other categories, such as dual (two), trial (three), and paucal (limited number). Alternative grammatical systems may also be used, although these are rare.
To identify the grammatical numbers available in a language, nouns and/or pronouns should be considered in nominative case (base form), as well as thirdperson verbs in active voice. The use of (N) or (V) after a grammatical number indicates that it is marked only on nouns or verbs, respectively. The use of parentheses around a grammatical number indicates that the number appears only very rarely.
NoGrNum: The language does not have grammatical number.
Pl: The number system is limited to singular and plural.
DuPl: The number system consists of singular, dual, and plural.
Du(N)Pl: The number system consists of singular and plural; the use of dual is limited to nouns.
Du(V)Pl: The number system consists of singular and plural; the use of dual is limited to verbs.
(Du)Pl: The number system consists of singular, dual, and plural, but the use of dual is limited.
(Du)(N)Pl: The number system consists of singular, dual, and plural, but the use of dual is limited to nouns and only used in limited circumstances.
DuTrPl: The number system consists of singular, dual, trial, and plural.
PauPl: The number system consists of singular, paucal, and plural.
SpecGrNum: An alternative grammatical number system exists that cannot be described with the Du, Tri, Pau, and Pl symbols or any combinations thereof. (Special explanation is required.)
 Types of grammatical marking can vary greatly; for more, see the parameter Number marking on nouns.
 Only productive grammatical numbers should be counted; numbers whose usage is rare and archaic should not be considered.
 If only one form exists for singular nouns or verbs, and the plural is expressed by means other than explicitly grammatical strategies — for example, numerals or reduplication — then the language is considered to have no grammatical number system. It should not be categorized as only marking the singular, since there is no obligatory grammatical contrast between singular and nonsingular. Existence of the singular alone does not constitute a separate parameter value, since all number systems by definition display a contrast between the singular and nonsingular numbers.
 It is theoretically possible for symbols other than Pl to stand alone as parameter values. For example, a language with the value Du would only mark the dual, with no marking for numbers greater than two; the latter would instead overlap with the singular.
 Combinations that are not listed here can also be formed according to the system above.