Just as subject, verb, object, complement, etc. are elements of the syntactic and functional patterning of a sentence, units can also be proposed and identified for the semantic analysis of essential elements of the sentence. These semantic elements of the sentence are most frequently represented in terms of a structure broken down into participants or arguments, and a relational element, which links the arguments, here called the verb, as exemplified in the following sentence:
Mary likes linguistics.
Mary and linguistics are arguments, while likes is the verb.
In order to avoid ambiguity present in natural language, linguists use special terms. The language used for a description of natural language, i.e. object language, in this context is referred to as metalanguage. Elements of this metalanguage include labels for participants or arguments, typically represented by noun phrase, such as AGENT, PATIENT, INSTRUMENT, EXPERIENCER, BENEFACTIVE or RECIPIENT, LOCATIVE, TEMPORAL or CAUSE. These labels are also called ‘semantic’ or ‘thematic roles’.