# Grammar Mixins

Xtext supports the reuse of existing grammars. Grammars that are created via the Xtext wizard use org.eclipse.xtext.common.Terminals by default which introduces a common set of terminal rules and defines reasonable defaults for hidden terminals.

`grammar org.xtext.example.MyDsl with org.eclipse.xtext.common.Terminals
generate myDsl 'http://www.xtext.org/example/MyDsl'
... some rules
`

Mixing in another grammar makes the rules defined in that grammar referable. It is also possible to overwrite rules from the used grammar.

Example :

`grammar my.SuperGrammar
...
RuleA : "a" stuff=RuleB;
RuleB : "{" name=ID "}";
grammar my.SubGrammar with my.SuperGrammar
Model : (ruleAs+=RuleA)*;
// overrides my.SuperGrammar.RuleB
RuleB : '[' name=ID ']';
`

Note that declared terminal rules always get a higher priority then imported terminal rules.