There is not a common definition of the term capability. In “Joint Capabilities Integration and Development System”, published by USA Department of Defense, a capability is defined as the ability to achieve a desired effect under specified standards and conditions through combinations of means and ways to perform a set of tasks.  The main capability inputs are: Doctrine, Organization, Training, Materiel, Leadership and Education, Personnel and Facilities (DOTMLPF).

The Canadian Collaborative Capability Definition, Engineering and Management Technology Demonstration Program (CapDEM TDP) defines a capability as the ability and the capacity to perform a set of tasks supporting a Defense Capability Area.  In accordance with CapDEM TDP a capability is a function of personnel, materiel facilities (real property, installations, utilities etc.) and procedures each of which are delivered through a schedule of managed processes across all of the PRICIE (Personnel, R&D/Ops Research, Infrastructure & Organization, Concepts, Doctrine & Collective Training, IT Infrastructure, Equipment, Supplies and Services) components.

According to the Australian Capability Development Group (CDG), a capability is the power to achieve a desired operational effect in a nominated environment, within a specified time, and to sustain that effect for a designated period. Capability is generated by fundamental inputs to capability comprising organization, personnel, collective training, major systems, supplies, facilities, support, command and management.

In line with the definitions stated, capability can be defined as an ability and capacity to perform tasks and achieve desired effects under specified standards and conditions in order to accomplish defined objectives. Ability means the quality that permits or facilitates fulfillment of a task and achievement of effects and objectives. On the other side, the term capacity is related to a quantity of capabilities.