When a supreme court justice agrees with the decision reached by the court in a case, but not with the reasons why the court made the decision, they may choose to write a: ?

Concurring opinion.

A concurring opinion is an opinion written by a Supreme Court justice who agrees with the decision and who the case went to, but may want to add to or comment on part of the decision. On the other hand, a dissenting opinion is by a judge who did not agree with the court decision, and writes down why he/she disagreed.