# functional

Pronunciation: say "FUNGK-shuh-nuhl" /ˈfʌŋkt͡ʃənəl/

## Adjective

1. Having a practical use; able to perform the job it exists for.
   - Simple: Useful and good at doing the job it was made 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._
2. Working as intended, with nothing broken or out of order.
   - Simple: Working properly and ready to use.
   - _The engineers confirmed that all backup systems were functional before the launch._
   - _Despite its age, the old tractor remains fully functional._
3. Relating to a function or functions in mathematics.
   - Simple: Having to do with a math function or functions.
   - _The model describes the functional dependence of pressure on temperature._
   - _Students learned functional notation before tackling calculus._
4. Intended for usefulness alone, without decorative concerns, especially in architecture.
   - Simple: Made only to be useful, not to look nice.
   - _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._
5. Relating to one's role, office, or official duties.
   - Simple: Having to do with someone's job or official role.
   - _He spoke at the ceremony in his functional capacity as chairman._
   - _The visit was functional rather than personal, tied entirely to her office._
6. Describing symptoms that affect how the body works without any change to its physical structure.
   - Simple: Describing symptoms that happen without any physical damage to the body.
   - _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._
7. Describing a programming style whose behavior is defined purely through mathematical functions, without side effects.
   - Simple: Describing a style of computer code built from math-like functions that change nothing outside themselves.
   - _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._

## Noun

8. In linear algebra, a linear map from a vector space to its field of scalars.
   - Simple: In math, a rule that takes a whole vector and gives back a single number.
   - _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._
9. A function whose argument ranges over a space of real- or complex-valued functions and whose value lies in a one-dimensional space.
   - Simple: In math, a rule that takes a whole function as its input and gives back a single number.
   - _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._
10. An object that wraps a function pointer or equivalent, so it can be stored and called like a function.
   - Simple: In programming, an object that holds a function so it can be passed around and called.
   - _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._

## Origin

Formed from "function" combined with the suffix "-al".

Source: DictionaryAI, https://dictionaryai.com/define/functional (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).