Functional
Functional refers to the ability of a system, component, or an individual to perform the specific tasks or functions that it was designed for. In the context of psychology, functional refers to a person's ability to perform daily living activities and participate in the community. In terms of systems and components, functional refers to the ability of the system or component to perform its intended function without any defects or malfunctions. In engineering, functional requirements refer to the specific characteristics that a system or component must possess to perform its intended function. Functionality refers to how a system or component is designed and organized. For example, a functional design refers to the design of a system or component in which the various parts are arranged logically and efficiently. This allows the system or component to perform its intended function effectively and efficiently. Functionalism can also refer to the way an individual interacts with the environment. Functional assessment evaluates an individual's abilities and limitations regarding their ability to perform activities of daily living and participate in the community. This assessment is used to determine how to support the individual best to improve their functional abilities. In summary, functional refers to the ability of a system, component, or individual to perform the specific tasks or functions that it was designed for. It can refer to the ability of a person to perform the activities of daily living, the ability of a system or component to perform its intended function without any defects or malfunctions, and how a system or component is designed and organized. How an individual interacts with the environment [Green C. & Hitzig, S. L.] In mathematics, a function (as a noun) is a particular type of function. The exact definition of the term varies depending on the subfield. In linear algebra, it is synonymous with linear forms, which are linear mapping from a vector space V into its field of scalars (that is, an element of the dual space V*) [Lang, p. 142]. Functional analysis and related fields generally refer to a mapping from a space X into the field of real or complex numbers [Kolmogorov, p. 77].
Green C., & Hitzig, S. L. (2009). Functional assessment in rehabilitation. Philadelphia: F.A. Davis.
Kolmogorov, Fomin. (1957). A numerical function f(x) defined on a normed linear space R will be called a functional. A functional f(x) is said to be linear if f(αx + βy) = αf(x) βf(y) where x, y ∈ R and α, β are arbitrary numbers.
Lang. (2002). Let E be a free module over a commutative ring A. We view A as a free module of rank 1 over itself. By the dual module E∨ of E we shall mean the module Hom(E, A). Its elements will be called functionals. Thus a functional on E is an A-linear
ISO/IEC/IEEE. (2015). Systems and software engineering.