Users can define their own entities in a DTD

NAME is the entity name and DEFINITION is the entity definition

There are two kinds of entities in XML documents:

1.General entities

Used in the context of documents

References to general entities start with & and end with;

2.Parameter entities

Used in a document’s DTD

References to parameter entities start with % and end with ;

Entities can be declared internal, or external

An internal entity is defined completely inside the XML document that references it (the document itself is an entity in XML).

External entities derive their content from an external source such as a file. References to external entities include URI (uniform resource identifier) at which they can be found

Contents of parsed entities are well formed XML texts

Unparsed entities hold data that user don’t want to be parsed