Enumerated

In computer science, an enumerated type is a data type consisting of a limited set of named values.

In HTML, enumerated attributes are attributes with a limited, predefined set of text values. For example, the global HTML dir attribute has three valid values: ltr, rtl, and auto. Like for HTML tag names, HTML enumerated attributes and their values are case-insensitive, so LTR, RTL, and AUTO will also work. The IDL-reflected property, HTMLElement.dir, can also be set using a case-insensitive value, but will always return the canonical format of the value defined in the specification (lowercased values in this example). See Attribute reflection for more information.