A relativizer is a °form that marks a °clause as being a °relative clause.
A relativizer can have the same shape as a complementizer, i.e. one and the same form can be simultaneously a relativizer and a complementizer. A synonym is "relative marker".
relativizer (STR) = a form that signals that an action is being used as a modifier – that is, it signals a relative clause. Example: in I ate the cheesecake [that Carol baked], that is the relativizer. A relativizer makes a relative clause construction syndetic. (Section 19.2.1)