In contrast to a sponsor, a "cosponsor" is a senator or representative who adds his or her name as a supporter to the sponsor's bill. An "initial cosponsor" or "original cosponsor" is a senator or representative who was listed as a cosponsor at the time of a bill's introduction, rather than added as a cosponsor later on.[1] A cosponsor added later is known as an "additional cosponsor".[2]