Effectiveness or effectivity is the capability of producing a desired result or the ability to produce desired output. When something is deemed effective, it means it has an intended or expected outcome, or produces a deep, vivid impression.
The origin of the word effective stems from the Latin word , which means "creative, productive, or effective". It surfaced in Middle English between 1300 and 1400 AD.
In mathematics and logic, effective is used to describe metalogical methods that fit the criteria of an effective procedure.
In group theory, a group element acts effectively (or faithfully) on a point, if that point is not fixed by the action.
In physics, an effective theory is, similar to a phenomenological theory, a framework intended to explain certain (observed) effects without the claim that the theory correctly models the underlying (unobserved) processes.
In heat transfer, effectiveness is a measure of the performance of a heat exchanger when using the NTU method.
In medicine, effectiveness relates to how well a treatment works in practice, especially as shown in pragmatic clinical trials, as opposed to efficacy, which measures how well it works in explanatory clinical trials or research laboratory studies.
In management, effectiveness relates to getting the right things done. Peter Drucker reminds us that "effectiveness can and must be learned".
In human–computer interaction, effectiveness is defined as "the accuracy and completeness of users' tasks while using a system".
In military science, effectiveness is a criterion used to assess changes determined in the target system, in its behavior, capability, or assets, tied to the attainment of an end state, achievement of an objective, or creation of an effect, while combat effectiveness is: "...the readiness of a military unit to engage in combat based on behavioral, operational, and leadership considerations. Combat effectiveness measures the ability of a military force to accomplish its objective and is one component of overall military effectiveness.