Security is protection from, or resilience against, potential harm (or other unwanted coercion) caused by others, by restraining the freedom of others to act. Beneficiaries (technically referents) of security may be of persons and social groups, objects and institutions, ecosystems or any other entity or phenomenon vulnerable to unwanted change. Refugees fleeing war and insecurity in Iraq and Syria arrive at Lesbos Island, supported by Spanish volunteers, 2015 Security mostly refers to protection from hostile forces, but it has a wide range of other senses: for example, as the absence of harm

On the individual level, security is most often understood as safety. This safety includes freedom from harm, whether physical or psychological. Threats to an individual's security can produce the fear or anxiety mentioned above. The United Nations Universal Declaration of Human Rights states that all people are entitled to "security of person." This declaration reinforces the concept of freedom from physical and psychological harm. Yet, what measures will be taken to protect an individual from harm? The most common forms of protection are legal structures that protect individuals from threats to their security. These include, but are not limited to, laws against murder, sex crimes, bodily harm, theft, and psychological harm such as coercion. The state assumes responsibility for constructing and implementing these legal regulations. In addition, security can be related to one's ability to attain the fundamental physical needs of a home, food, and socio-economic needs such as a job. The concept of individual security can therefore be linked to an individual's perception of her or his standard of living. The individual may thus equate security with a high standard of living.

The simplest concept of security at the regional level could be economic, implying protection of regional interests. Perhaps a regional association with, or ownership of, a valued resource could provoke desires for security, and the responsibility for protecting that security would rest on the region. For example, labor or trade unions perform this function. Other notions of security at this level could be to maintain a certain standard of living. In this realm, members of a regional group might want to protect themselves from mass immigration, which could occur due to the region's coveted resources. The region might seek to ensure its security by campaigning against this immigration. Threats to security are often cited here, usually connected to issues of lowered living standards. On a more subtle level, religious, national, or ethnic groups may shrewdly promote their interests under the guise of regional security, and may elevate their group security to a regional priority level.

Global security is a relatively new concept, and conjures up images of organizations such as the United Nations. Global security, however, may be undermined by national security concerns; if one nation feels threatened by another, then global security cannot exist since members of the world are in disagreement. Global security is also undermined by negative judgment by one nation of another's philosophy of government. If nation A decides that nation B's governing methods are wrong, nation A will not submit to a global authority that allows nation B's methods to continue. Global security is thus a weak concept, since it assumes a supranational entity to whose judgment nations would yield in matters of disagreement. This is obviously a far-fetched goal, which is unlikely to be realized in the near future. As resources such as land, water, and oil are increasingly coveted by nations, global security has little chance to emerge as a durable concept in international relations.