An obligor—a person who becomes obligated, under a Commercial Paper, such as a promissory note or check—by signing the instrument in conjunction with the original obligor, thereby promising to pay it in full.
The cosigner may be held equally responsible for the payment of the debt or may be required to pay only upon the failure of the original obligor to do so, depending upon state law and the terms of the agreement that also determine the rights of the cosigner.
Cosigner is synonymous with the term comaker.