Dropdown menu
A floating list of actions anchored to a trigger. Row actions, "More" buttons, account menus all live here.
Canonical menu primitive.
Per audit-reuse D-5, .dropdown is the canonical class for floating action lists. The legacy .menu, .context-menu and .user-menu classes still ship as deprecation aliases; treat them as .dropdown, .dropdown.dropdown--compact and .dropdown.dropdown--user in new code.
Default
Floating list, popover shadow, hairline border. Hover row in surface-muted.
With groups
Group headers in caption tone, separator between groups.
With checkable items
Filter dropdowns; current selections show a check.
Do & don't
Group items. A long flat list of 12 actions is impossible to scan.
Open a dropdown on hover. Always click-to-open.
Put dangerous actions at the bottom and colour them — separated by a divider.
Use a dropdown for navigation between pages. Use a sidebar.