Grammatical functions, such as subject and object, should not be confused with thematic roles, such as agent or patient, which convey semantic functions instead. It is true that syntactic grammatical functions systematically relate to semantic roles. For example, in active clauses where the verb has an agent and a patient, the agent will always be the subject and the patient the object, as shown in the example below, where the grammatical subject gianni also overlaps with the semantic role of the agent of the sentence, and conversely the grammatical object nail overlaps with the semantic function of the patient.
gianni nail CL(closed G): ‘hit_with_hammer’++
‘Gianni hammers a nail.’
However, the combination of grammatical and semantic functions is not always univocal. Indeed, there are many cases where the syntactic subject overlaps with other semantic roles, as for example in the sentence below where the grammatical subject (win^person) overlaps with the semantic role of the recipient:
win^persona prize CL(closed 5): ‘give_prize’3a receive3a
‘The winner received an award.’
LIS is a language with a relatively flexible word order (SYNTAX 2.3) and thus distinguishing grammatical functions can be more difficult than in languages which display a more fixed word order. Moreover, morphological case markers and agreement strategies (LEXICON 3.2.2) are not obligatory will all verbs in LIS. Still, it seems that grammatical functions can be distinguished in LIS through verb agreement.