Reciprocity is the idea of mutual give-and-take, like if you give me your notes from the class I missed, I'll bake you cookies as reciprocity.

Tennessee and Illinois do not have real estate licensing reciprocity. You must wait until after your move.

You can find general basic information on reciprocity on Wikipedia. Some books on reciprocity are: Reciprocity, by Lawrence Baker, A cooperative species: Human reciprocity by Lawrence Baker, Trust and Reciprocity: Interdisciplinary Lessons for experimental research, by Elinor Ostrom.

Does virginia have reciprocity for tickets with delaware?

in the fraction 9/10 the positive reciprocity is 9