Basically, every type of government organization defines the defence system with functions that provide deterrence from threats, as well as countering various types and forms of threats to main social values. The subject of this paper is the national security strategy, i.e. security challenges, risks and threats that are essential for the fulfilment of the highest state security interests. The author has analysed the main categories of national security theory: "danger", "challenge", "risk" and "threat". On the basis of the definition and comparative analysis of these categories, presented in different sources, he reveals their content and essence and comes to the conclusion that, despite the semantic similarity of the categories "challenge", "risk and "threat", each of them defines a different degree of threat, that is, damage. Accordingly, it has been noticed that the National Security Strategy of the Republic of Serbia does not make a distinction between security challenges, risks and threats, but speaks of them as a single syntagm and category. Since this document is the basis for the integrated activities of the defence forces, in the function of protecting vital national interests, the considered issue indicates the importance of as precise definition of SCRT as possible because inaccurate definition could prevent an adequate response when some of security challenges, risks and threats manifest themselves on security object references. On the basis of the definition and comparative analysis of the definitions of these categories, mentioned in different sources, it can be concluded that, despite the semantic similarity of the categories "challenge", "risk and "threat", each of them defines a different degree of threat, that is, harmful consequences. The subject of this paper has been to make a distinction between SCRT in order to improve the methodology for identifying and assessing military and non-military challenges, risks and threats when developing the National Security Strategy and other strategic and doctrinal documents. Accordingly, in reality, dynamics from several security sectors (political, military, economic, social, ecological and informational) is intertwined in most security problems. The analytical framework of the sectoral approach of the Copenhagen School has been proposed for the analysis of manifest forms of threats to national security. The implementation of the analytical framework is possible within the multicriteria mathematical model. Since risk is a measurable value, the implementation of this concept increases the objectivity of the identification and assessment of SCRT for state security. This approach is important not only in terms of defining national security policy and defence policy, but also has the greatest impact on the development plans of the defence system as a whole, particularly the development of the capabilities of the Serbian Armed Forces.