expression

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expression

1. communication of emotion through music, painting, etc.
2. Maths a variable, function, or some combination of constants, variables, or functions
3. Genetics the effect of a particular gene on the phenotype
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

expression

[ik′spresh·ən]
(chemical engineering)
Separation of liquid from a two-phase solid-liquid system by compression under conditions that permit liquid to escape while the solid is retained between the compressing surfaces. Also known as mechanical expression.
(computer science)
A mathematical or logical statement written in a source language, consisting of a collection of operands connected by operations in a logical manner.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

expression

(programming)
Any piece of program code in a high-level language which, when (if) its execution terminates, returns a value. In most programming languages, expressions consist of constants, variables, operators, functions, and parentheses. The operators and functions may be built-in or user defined. Languages differ on how expressions of different types may be combined - with some combination of explicit casts and implicit coercions.

The syntax of expressions generally follows conventional mathematical notation, though some languages such as Lisp or Forth have their own idiosyncratic syntax.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)