Explanation:
In
mathematics, an expression is a finite combination of symbols that are well-formed according to the rules
applicable in the context at hand. Symbols can designate values (constants), variables, operations, relations, or can constitute
punctuation or other syntactic entities.
In algebra an expression may be used to
designate a value, which value might depend on values assigned to variables occurring in the expression;
the determination of this value depends on the semantics attached to the symbols of
the expression. (Our solved example in
mathguru.com uses this concept)
These semantic
rules may declare that certain expressions do not designate any value; such
expressions are said to have an undefined value, but they are well-formed
expressions nonetheless. In general the meaning of expressions is not limited
to designating values; for instance, an expression might designate a condition,
or an equation that is to be solved, or it can
be viewed as an object in its own right that can be manipulated according to
certain rules.
Variables
Many mathematical expressions include letters called variables. Any variable can be
classified as being either a free
variable or a bound variable.
For a given combination of values for the free variables, an
expression may be evaluated, (Our solved example in mathguru.com uses this concept)
Although for some combinations of values of the free variables,
the value of the expression may be undefined. Thus an expression represents a function whose inputs are the value assigned
the free variables and whose output is the resulting value of the expression.
For example,
the expression
x / y
evaluated for x = 10, y =
5, will give 2; but is undefined for y = 0.
http://en.wikipedia.org/wiki/Expression_(mathematics)
The above explanation is copied from
Wikipedia, the free encyclopedia and is remixed as allowed under the Creative
Commons Attribution- ShareAlike 3.0 Unported License.