What refers to functional paradigm?

Functional programming is a programming paradigm in which we try to bind everything in pure mathematical functions style . It is a declarative type of programming style. Its main focus is on “what to solve” in contrast to an imperative style where the main focus is “how to solve”.31 Ağu 2021

An illustration of Parson’s four-function paradigm: (a) latent pattern-maintenance, (b) integration, (c) adaption, and (d) goal attainment . The four functions of actions form a general paradigm for all system.

Strictly speaking, Functional programming is a programming paradigm in which we code the computer program as the evaluation of expressions same as mathematical functions (No changing-state and mutable data).