From http://www.w3schools.com (Copyright Refsnes Data)

DTD - Entities

Entities are variables used to define shortcuts to standard text or special characters.

• Entity references are references to entities

• Entities can be declared internal or external

An Internal Entity Declaration

Syntax

<!ENTITY entity-name "entity-value">

Example

DTD Example:

<!ENTITY writer "Donald Duck.">
<!ENTITY copyright "Copyright W3Schools.">

XML example:

<author>&writer;&copyright;</author>

Note: An entity has three parts: an ampersand (&), an entity name, and a semicolon (;).

An External Entity Declaration

Syntax

<!ENTITY entity-name SYSTEM "URI/URL">

Example

DTD Example:

<!ENTITY writer SYSTEM "http://www.w3schools.com/entities.dtd">
<!ENTITY copyright SYSTEM "http://www.w3schools.com/entities.dtd">

XML example:

<author>&writer;&copyright;</author>

From http://www.w3schools.com (Copyright Refsnes Data)