+Referential transparency means an expression can be replaced by its value without altering a program's outcome. It is a cornerstone of [Functional Programming](/wiki/functional_programming), where [Pure Functions](/wiki/pure_functions) avoid side effects, ensuring predictable behavior. This clarity simplifies reasoning and testing.
+## See also
+- [Side Effect](/wiki/side_effect)
+- [Immutability](/wiki/immutability)
+- [Declarative Programming](/wiki/declarative_programming)