An argument is a constituent in the domain of a lexical head H that is selected by H. An argument is distinct from an adjunct, which is a constituent not selected by H. Arguments and adjuncts differ in that the former are normally obligatorily present (or at least semantically implied), whereas adjuncts are optional. In (i), the noun phrase de aardappelen'the potatoes' is virtually obligatory and can be considered an argument of the verb schillen'to peel', whereas the PP in de keuken'in the kitchen' is optional and can be considered an adjunct.

Arguments are usually associated with verbs: verbs have argument structures, specifying the number and thematic roles of their arguments. An intransitive verb like lachen'to laugh,' for example, has one (agentive) argument, a transitive verb like lezen'to read' has two arguments, an agent and a theme, and a ditransitive verb like geven'to give' has three arguments. The arguments of these verbal predicates fill slots in the predicate frame implied by these verbs: lachen is a one-place predicate lachen (x) and the agentive argument fills the single argument slot; lezen is a two-place predicate lezen (x,y) and the two arguments fill the two slots in the predicate frame; geven is a three-place predicate and again the three arguments fill the slots in the predicate frame geven (x,y,z).

The arguments in the predicate frame of two- and three-place predicates are not all of the same nature: filling the y and z slots in a sense completes the predicate, as a result of which it can be predicated of the argument placed in the x slot. In syntactic terms, the argument filling the x slot of a predicate normally corresponds to the subject of the clause, whereas the arguments filling the y and z slots correspond to the objects of the clause. Since the objects have the function of creating a complete predicate, they are often referred to as the complements or internal arguments of the verb. The subject, on the other hand, will be referred to as the external argument of the verb, the argument which the complete verbal predicate is predicated of. In the lexical frames in (ii), the external argument is underlined in order to distinguish it from the complements. Note that there are several complications that are not discussed here: for instance, unaccusative verbs are assumed not to have an external argument but to be predicated of their internal argument (cf. V2.1).
      Since adjectives and nouns function as predicates as well, they also take arguments. This is shown in (iii), where the adjectival/nominal noun phrase is predicated of the noun phrase Jan, which therefore functions as the first argument. Since the usual labels for semantic roles are created especially for expressing the roles of the arguments in the event structure denoted by verbal predications, we will simply refer to the first argument of non-verbal predicates as the referent (Ref), that is, the entity with regard to which the property denoted by the adjectival/nominal noun applies.