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# expression

An *expression* is a symbol or combination of symbols used to denote a quantity or value. Expressions consist of constants, variables, operations, operators, functions, and parentheses.

Note 1. If an expression contains one or more operations to be performed in a certain order, the expression may be named after the last (i.e. outermost) operation. For example, the expression $\displaystyle a^{2}-5\sqrt{a}+\frac{2}{3a}$ is a sum expression.

# References

- 1
*Dictionary.com Unabridged*(version 1.1). Accessed on February 22, 2008. URL: http://dictionary.reference.com/browse/expression

Defines:

sum expression

Related:

Equation

Type of Math Object:

Definition

Major Section:

Reference

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## Mathematics Subject Classification

00-01*no label found*

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## Comments

## MSC for expression?

I am slightly baffled as to which MSC's are applicable for this entry. If you have any suggestions, please let me know or add them yourself. Thanks.

## Re: MSC for expression?

I think the easiest answer is: delete the entry. This is not a mathematical definition, it is simply the definition of a word. Planetmath is not a dictionary of the English language and entries like this, in my opinion, do not add any value and only clutter the linking system.

Alvaro

## Re: MSC for expression?

Actually, I added the entry in response to a request. Also, the mathematical usage of "expression" is somewhat different from its usage outside of mathematics. I need more time (and hopefully input from others) before making a decision about this entry.

Warren

## Re: MSC for expression?

Yes, it does seems useful to have one or more formal definitions. Various definitions will be found in the computer science literature, where solid definitions of things like m-expressions and s-expressions are needed to formalize combinator expressions and lambda calculus expressions.

## Re: MSC for expression?

I agree, this could become a very useful entry to have. For one thing, it could give an overview of what kinds of symbol strings are considered valid expressions by computer algebra systems, scientific and graphing calculators, RPN calculators, etc. It would also make sense to mention operator precedence. That's my two cents on this.