| --- |
| page_title: Expressions - Configuration Language |
| description: >- |
| An overview of expressions to reference or compute values in Terraform |
| configurations, including types, operators, and functions. |
| --- |
| |
| # Expressions |
| |
| > **Hands-on:** Try the [Create Dynamic Expressions](https://learn.hashicorp.com/tutorials/terraform/expressions?in=terraform/configuration-language&utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) tutorial. |
| |
| _Expressions_ refer to or compute values within a configuration. |
| The simplest expressions are just literal values, like `"hello"` or `5`, |
| but the Terraform language also allows more complex expressions such as |
| references to data exported by resources, arithmetic, conditional evaluation, |
| and a number of built-in functions. |
| |
| Expressions can be used in a number of places in the Terraform language, |
| but some contexts limit which expression constructs are allowed, |
| such as requiring a literal value of a particular type or forbidding |
| [references to resource attributes](/language/expressions/references#references-to-resource-attributes). |
| Each language feature's documentation describes any restrictions it places on |
| expressions. |
| |
| You can experiment with the behavior of Terraform's expressions from |
| the Terraform expression console, by running |
| [the `terraform console` command](/cli/commands/console). |
| |
| The other pages in this section describe the features of Terraform's |
| expression syntax. |
| |
| - [Types and Values](/language/expressions/types) |
| documents the data types that Terraform expressions can resolve to, and the |
| literal syntaxes for values of those types. |
| |
| - [Strings and Templates](/language/expressions/strings) |
| documents the syntaxes for string literals, including interpolation sequences |
| and template directives. |
| |
| - [References to Values](/language/expressions/references) |
| documents how to refer to named values like variables and resource attributes. |
| |
| - [Operators](/language/expressions/operators) |
| documents the arithmetic, comparison, and logical operators. |
| |
| - [Function Calls](/language/expressions/function-calls) |
| documents the syntax for calling Terraform's built-in functions. |
| |
| - [Conditional Expressions](/language/expressions/conditionals) |
| documents the `<CONDITION> ? <TRUE VAL> : <FALSE VAL>` expression, which |
| chooses between two values based on a bool condition. |
| |
| - [For Expressions](/language/expressions/for) |
| documents expressions like `[for s in var.list : upper(s)]`, which can |
| transform a complex type value into another complex type value. |
| |
| - [Splat Expressions](/language/expressions/splat) |
| documents expressions like `var.list[*].id`, which can extract simpler |
| collections from more complicated expressions. |
| |
| - [Dynamic Blocks](/language/expressions/dynamic-blocks) |
| documents a way to create multiple repeatable nested blocks within a resource |
| or other construct. |
| |
| - [Type Constraints](/language/expressions/type-constraints) |
| documents the syntax for referring to a type, rather than a value of that |
| type. Input variables expect this syntax in their `type` argument. |
| |
| - [Version Constraints](/language/expressions/version-constraints) |
| documents the syntax of special strings that define a set of allowed software |
| versions. Terraform uses version constraints in several places. |
