Broadly, assessment is concerned with the identification of distinguishing features of individual cases, whereas classification is concerned with the grouping of cases according to their distinguishing features. When people with emotional or mental problems seek your professional help, you would need to have adequate knowledge of mental problems or disorders and a systematic approach to assessment. Taking a step-by-step approach to assessment helps to establish the problem and its impact on various aspects of the person’s life; and in decisions regarding the next steps in managing the problem. 
4.1 CLASSIFICATION OF MENTAL DISORDERS
When you assess a client, you try to interpret her or his problems in terms of known disorders and assign a label (diagnosis) to the problems she or he is facing. These diagnoses are arranged according to groups of disorders within classificatory systems. 
4.1.2  Utility of Classificatory Systems
Knowing the classificatory system can help you in several ways: 
1) Giving a client a diagnosis can help you to decide about her or his management, as standardised management strategies are known for many diagnoses. 
2) A diagnosis (which in essence is a summary of clinical information) can help you to predict the course and outcome of the problems the individual is facing. 
3) A diagnosis can help you in communicating efficiently with other professionals who follow the same classificatory system, regarding the client’s problems. 
4) Diagnoses and classificatory systems can help you to group together (and analyse) individuals with similar set of problems, and thus help you with research.