Carryover refers to a situation where the effects obtained in one phase appear to carry over into the next phase. The term carryover is generally used in the context of  removal designs. Thus, if you attempted to remove a successful intervention to recreate a sound baseline to determine whether your intervention was actually affecting the problem, and the problem remained unchanged despite the removal, carryover effects would pertain. Carryover effects might also be produced by totally extraneous outside influences having some impact on the target problem.
