LSF uses both manual and non-manual markers to identify relative clauses. There are two different relative pronouns signs: ‘person-cl’ and ‘pi’.
'person-cl' is for human referents only and is used in appositive relative clauses [Syntax- Section 3.4.7]. An example is provided below.
rel
ix1 prefer little girl person-cl pet dog.
'I prefer the little girl, who pets the dog.' (Hauser, 2019)
The second relative pronoun is the demonstrative sign glossed as 'pi' after the mouthing element marking it. The relative pronoun 'pi' is used for restrictive relative clauses and any type of head, whether human, non-human or inanimate, as shown in the following examples.
rel
a. ix1 prefer vet pi cure dog.
'I prefer the vet who cures the dog.'
rel
b. ix1 prefer dog pi man pet.
'I prefer the dog which the man pets.
rel
c. ix1 prefer napkin pi cover lighter.
'I prefer the napkin which covers the lighter.' (Hauser, 2019)
Both relative pronouns come with a specific set of non-manual markings over them: a) at least one part of the upper body —shoulders or torso— is oriented towards the locus where the head of the relative is located in the signing space; b) eyebrows are raised; c) lips are tensed and d) chin is pointed upwards or downwards. What seems to matter the most is the contrast between the head of the relative clause and the rest of the relative clause.
A relative clause does not need to be introduced by a relative pronoun. The non-manual markers over the head noun suffice to identify the construction. This is illustrated in the following example.
rel
ix1 prefer vet cure dog.
‘I prefer the vet who cures the dog.’ (Hauser, 2019)