The Ceylon language module containing the core definitions referred to by the language specification, along with some basic functionality of use to most programs:

• The root package defines general-purpose functionality including support for numbers and character strings, streams and sequences, exceptions, and null values.
• The Ceylon metamodel is defined in ceylon.language.meta and its subpackages ceylon.language.meta.model and ceylon.language.meta.declaration, which define interfaces for interacting with applied types and unapplied type declarations respectively.

This module defines an abstraction over the basic facilities of the Java or JavaScript virtual machine, containing only functionality that can be easily implemented on both platforms. Thus, certain functionality, for example, concurrency, for which there is no common virtual machine-agnostic model, is not covered by the language module.

The language module is an implicit dependency of every other Ceylon module, and may not be explicitly imported.