Keyword crate

A Rust binary or library.

The primary use of the crate keyword is as a part of extern crate declarations, which are used to specify a dependency on a crate external to the one it's declared in. Crates are the fundamental compilation unit of Rust code, and can be seen as libraries or projects. More can be read about crates in the Reference.

extern crate rand;
extern crate my_crate as thing;
extern crate std; // implicitly added to the root of every Rust project

The as keyword can be used to change what the crate is referred to as in your project. If a crate name includes a dash, it is implicitly imported with the dashes replaced by underscores.

crate is also used as in conjunction with pub to signify that the item it's attached to is public only to other members of the same crate it's in.

pub(crate) use std::io::Error as IoError;
pub(crate) enum CoolMarkerType { }
pub struct PublicThing {
    pub(crate) semi_secret_thing: bool,
}