Functional

Functional may refer to:
 * Movements in architecture:
 * Functionalism (architecture)
 * Form follows function
 * Functional group, combination of atoms within molecules
 * Medical conditions without currently visible organic basis:
 * Functional symptom
 * Functional disorder
 * Functional classification for roads
 * Functional organization
 * Functional training

In mathematics

 * Functional (mathematics), a term applied to certain scalar-valued functions in mathematics and computer science
 * Functional analysis
 * Linear functional, a type of functional often simply called a functional in the context of functional analysis
 * Higher-order function, also called a functional, a function that takes other functions as arguments

In computer science, software engineering

 * "Functional" (noun) may be used as a synonym for Higher-order function
 * functional (C++), a header file in the C++ Standard Library
 * Functional design, a paradigm used to simplify the design of hardware and software devices
 * Functional model, a structured representation of functions, activities or processes in systems and software engineering
 * Functional programming, a programming paradigm based on mathematical functions rather than changes in variable states
 * In an ontology (information science), "functional" is a property or relation that can only hold a single value for a given individual