functional

Pluralfunctionals

1. 1
   adjective

   Having a practical use; able to perform the job it exists for.

   The design is both beautiful and functional, serving its purpose without waste.

   She prefers functional furniture that earns its place in a small apartment.

   Similarpractical, useful, utilitarian, serviceable

   Oppositeimpractical, useless, decorative

   Note

   The everyday sense, the one that can stand beside artistic as a second virtue: a sculpture is functional too if it also serves as a hatrack. It differs from the "in working order" meaning, because a broken chair is still a functional kind of object. The word also forms set phrases such as functional fitness, exercise meant to keep people, older people especially, moving.

2. 2
   adjective

   Working as intended, with nothing broken or out of order.

   The engineers confirmed that all backup systems were functional before the launch.

   Despite its age, the old tractor remains fully functional.

   Similarworking, operational, operative, running

   Oppositebroken, inoperative, defective

3. 3
   adjective

   Relating to a function or functions in mathematics.

   The model describes the functional dependence of pressure on temperature.

   Students learned functional notation before tackling calculus.

   Note

   Mathematics gives this adjective its strictest meaning: a function is a mapping that assigns each input exactly one output, and what is functional is described through such a mapping. In phrases like functional dependence or functional notation it means "expressed as a function," not "working" or "useful." Keep it distinct from the noun "functional", which names a function whose argument is itself a function.

4. 4
   adjective

   Intended for usefulness alone, without decorative concerns, especially in architecture.

   The architect favored a functional style, stripping away ornament in favor of clean, purposeful lines.

   Their home is deliberately functional, every room shaped by how the family actually lives.

   Similarutilitarian, practical, plain, austere

   Oppositedecorative, ornamental, ornate

   Note

   Here usefulness is not one virtue among others but the whole program. The word implies that ornament has been left out on purpose. Architects and engineers use it this way, and a functional element is judged on technical demands rather than looks. The everyday "useful" meaning can sit beside beautiful as praise. This sense often marks the absence of beauty as a deliberate choice.

5. 5
   adjective

   Relating to one's role, office, or official duties.

   He spoke at the ceremony in his functional capacity as chairman.

   The visit was functional rather than personal, tied entirely to her office.

   Similarofficial

   Oppositepersonal, private

6. 6
   adjective

   Describing symptoms that affect how the body works without any change to its physical structure.

   The clinic specializes in functional disorders, where patients have real symptoms despite normal test results.

   He was diagnosed with a functional condition rather than structural heart disease.

   Oppositeorganic, structural

   Note

   Medicine sets this sense against organic: a functional disorder disturbs how an organ works, while an organic one changes what it is. Frank J. Hirschboeck's "Treatment of Functional Heart Disease" (1928) admits the line is hard to draw, since organic disease may begin as a disturbance of function. In psychology the idea stretches further, to how well a person manages daily life, from social activities to independence and work.

7. 7
   adjective

   Describing a programming style whose behavior is defined purely through mathematical functions, without side effects.

   Haskell is a purely functional language, treating computation as the evaluation of functions.

   They rewrote the module in a functional style to remove hidden side effects.

   Similarpure

   Oppositeimperative

   Note

   A computing term built on the mathematician's idea of a function: the same input always yields the same output, and nothing else changes along the way. Its synonym is pure. Its opposite is imperative, the style that works by changing stored state step by step. The two ideas combine in purely functional, the usual label for a language that admits no side effects at all.

8. 8
   nouncountable

   In linear algebra, a linear map from a vector space to its field of scalars.

   Every continuous functional on the space can be represented by an inner product with a fixed vector.

   The integral defines a linear functional on the space of continuous functions.

   Note

   Linearity is what this sense adds, and in return the inputs need not be functions at all, since any vector space will do. The full phrase is linear functional, often shortened to functional once the context is clear. These maps are among the central objects of functional analysis, where much of the theory concerns how a space and its functionals mirror each other.

9. 9
   nouncountable

   A function whose argument ranges over a space of real- or complex-valued functions and whose value lies in a one-dimensional space.

   The arc-length functional assigns to each curve the number measuring its length.

   Minimizing the energy functional yields the equation that the optimal path must satisfy.

   Note

   The definite integral is the textbook case: give it an integrable function on an interval and it returns a single number. Arc length and energy work the same way, which is why functionals matter wherever one looks for the function that makes such a quantity as small as possible. The plural is functionals, and the linear vector-space version is a close relative defined on any vector space.

10. 10
    nouncountable

    An object that wraps a function pointer or equivalent, so it can be stored and called like a function.

    The library accepts a functional that defines how two elements should be compared.

    They stored each callback as a functional in a list of handlers.

    Similarfunctor

    Note

    A programmer's noun, distinct from the mathematician's function of functions: the object stands in for a function so that code can store it, pass it along and call it later. The words "or equivalent" matter, because languages without raw pointers wrap their callable values in other ways. Do not confuse it with the functional programming style, since the noun says nothing about side effects.

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