A modifier keyword.

Note: The Ceylon Language Specification also refers to certain annotations, e. g. shared, abstract, variable, etc., as “modifiers” – see §7.4.1, Declaration Modifiers. In ceylon.ast, however, Modifier refers only to the reserved keywords that can be used on a function or value:

• void – VoidModifier
• dynamic – DynamicModifier
• function – FunctionModifier
• value – ValueModifier