You may have to adapt a treatment due to a contra-indication. For example, I had an IHM massage client who had recently broken an arm, so I omitted both arms. That would be adapting a treatment.
Another way of adapting a treatment might be, for instance, leaving out tapotement if a client wishes their massage to be relaxing. Or increasing kneading & tapotement if they wish to break down fatty tissue.
Hope that helps