# Expression
<a name="API_Expression"></a>

## Description
<a name="API_Expression_Description"></a>

A named expression that can be evaluated at search time. Can be used to sort the search results, define other expressions, or return computed information in the search results. 

## Contents
<a name="API_Expression_Contents"></a>

 **ExpressionName**   
Names must begin with a letter and can contain the following characters: a-z (lowercase), 0-9, and \$1 (underscore).  
Type: String  
 Length constraints: Minimum length of 1. Maximum length of 64.   
 Required: Yes 

 **ExpressionValue**   
The expression to evaluate for sorting while processing a search request. The `Expression` syntax is based on JavaScript expressions. For more information, see [Configuring Expressions](http://docs.aws.amazon.com/cloudsearch/latest/developerguide/configuring-expressions.html) in the *Amazon CloudSearch Developer Guide*.  
Type: String  
 Length constraints: Minimum length of 1. Maximum length of 10240.   
 Required: Yes