ARIA pattern
A documented composite widget design — combobox, tabs, dialog, listbox, menubar, tree — with conventional roles, states, properties, and keyboard interactions defined by the WAI-ARIA Authoring Practices Guide.
Following an ARIA pattern means adopting the role-state-keyboard contract specified for it. Deviation surprises users who learned the conventions on other sites; conformance lets the same keyboard sequence work everywhere. The APG patterns are the single best reference for what each role expects; about 16 patterns cover the vast majority of widgets shipped on the web.