# Glossary

Terms that have a special meaning or interpretation in Thrift.

## Specification Requirement Levels

Key terms used consistently throughout this specification to indicate the level
of requirement:

- **must** / **must not** - required
- **should** / **should not** - strongly encouraged
- **may** - optional

For more details regarding the meaning of these terms, see [rfc2119](https://www.ietf.org/rfc/rfc2119.txt).

## Kinds of Types

See dedicated sub-page: [Kinds of Types](./kinds-of-types.md).


## Release States

See [annotations/thrift.thrift](https://github.com/facebook/fbthrift/tree/main/thrift/annotation/thrift.thrift)

- [Experimental](https://github.com/facebook/fbthrift/tree/main/thrift/annotation/thrift.thrift#Experimental)
- [Beta](https://github.com/facebook/fbthrift/tree/main/thrift/annotation/thrift.thrift#Beta)
- Released
- [Deprecated](https://github.com/facebook/fbthrift/tree/main/thrift/annotation/thrift.thrift#Deprecated)
- [Legacy](https://github.com/facebook/fbthrift/tree/main/thrift/annotation/thrift.thrift#Legacy)