Shifting Terms and Concepts: From Defence to (Human) Security Introduction Over the last two decades, the concepts of defence and security have overlapped to the point where the former is merged with the latter. Since jihadist terrorism broke out at the dawn of the millennium, governments have been forced to review the classic paradigm according to which the military is employed in overseas operations—or the defence of the homeland from external enemies—and police and law enforcement agencies are tasked with internal security. In such a context, the military has taken on an increasing role in national security matters, although security itself is an umbrella concept under development that currently includes such cross- cutting topics as terrorism, cyber threats, health, food, energy, the economy, poverty, climate change, information technology, social security, job security, just to mention a few. The inclination to replace the idea of defence with security has contributed to the expansion of the idea of security itself. This way, defence activities abroad, such as military assistance to Ukraine in the context of the ongoing conflict with Russia, are presented to the public as "security" operations. Data analysis The author of this work has checked the multi-sectoral approach to security outlined by the UN and the NATO against commonly accepted versions of human security through a comparative study of the definitions provided by well-established and reputable dictionaries such as Merriam-Webster, Britannica, Collins, Oxford, Cambridge, Longman, and Macmillan. Such dictionaries provide similar definitions of the term "security": safety; safety from attack, harm, or damage; freedom from danger or threat; freedom from fear or anxiety; being safe and free from worry; being protected or safe from harm. Security is the protection from, or resilience against, the potential harm caused by others by restricting one's freedom to act. Conclusions The human security approach broadens the scope of security analysis and policy from the traditional notion of national security to the security of people and their complex social and economic interactions. The term "defence", is given as a synonym of "security" by the majority of these dictionaries (Merriam-Webster, Cambridge, Oxford, Collins), even though Britannica and Macmillan continue to be anchored to the dichotomy of defence/external and security/internal, respectively, by providing the words "national security" and "internal security", is evidence of this trend. The evolving concept of security must be scrutinised, with special attention paid to the notion of human security, boosted by UN General Assembly resolution 66/290 and the NATO Strategic Concept 2022, and currently under investigation by the Exploratory Team of the NATO Science and Technology Organization. So far, the meaning of “human security” remains unclear. References 1. United Nations Development Programme (UNDP), Human Development Report 1994: New Dimensions of Human Security, New York, UN, 1994. 2. UN General Assembly (UNGA), Follow-up to paragraph 143 on human security of the 2005 World Summit Outcome, resolution adopted on 25 Oct. 2012, A/RES/66/290, in GAOR, 66th sess., Suppl. no. 49. 3. NATO Heads of State and Government, Warsaw Summit Communiqué, 9 July 2016, Press Release (2016) 100. 4. NATO Heads of State and Government, London Declaration, 4 dec. 2019, Press Release (2019) 115. 5. NATO Heads of State and Government, Brussels Summit Communiqué, 14 June 2021, Press Release (2021) 086. 6. NATO Heads of State and Government, Madrid Summit Declaration, 29 June 2022, Press Release (2022) 095. 7. NATO Strategic Concept 2022, adopted at the Madrid Summit, 28-29 June 2022. 8. NATO, Human Security: Approach and Guiding Principles, https://www.nato.int/cps/en/natohq/official_texts_208515.htm?s electedLocale=en. 9. Marsili, Marco, The Role of the Armed Forces in Homeland Security, in Book of Abstracts of the XI Portuguese Con