One who attests.
A person who interprets.
A program that executes another program written in a high-level language by reading the instructions in real time rather than by compiling it in advance.
A person who converts spoken or signed language into a different language for the benefit of one or more others who do not understand the first language being used (especially if in real time or shortly after that person has finished communicating). (Contrasted with translator.)
A guide who helps people visiting an attraction such as an art exhibit, a nature reserve, etc., understand what they are seeing.
Something that reveals or clarifies.