Dropdown
Dropdown opens a short list of options, anchored to the control that opened it.
Preview
A menu anchored to a trigger. Press the label to open it. Past about six options on a phone, use Action Sheet or Picker instead.
Closed, the trigger has no fill at all. Open, it takes bg/soft-100 and the caret flips from down to up. 296 is arithmetic: 12 of padding, the 32 title, four 56 rows, four 4 gaps, 12 again. The label does not move while that happens: in the file the open menu is positioned absolutely inside the component, so the trigger measures 106 by 44 either way, and here the wrapper is held at the menu's own 300 so the label keeps its left edge.
Option
The building block behind every row, not for direct use. Four states, three of them just a fill. Checked adds a brand tick on the right.
Pressed is darker than Active here, the reverse of Context Menu, where Pressed takes bg/weak-50. The title and description sit at gap 0, so 24 over 20 fills the 44 the row leaves after its padding.
Only Popover
The second axis drops the trigger and ships the menu alone, for anchoring to something the component does not own: an icon button, a row, a long press.
Only three of the four axis pairs exist. A closed popover would be nothing on screen, so the file does not draw it.
Properties
Two axes and a boolean on the published component, four more on the option inside it.
DropdownMenu ships 3 variants, not 4: a closed popover would be nothing on screen. The option ships 4 and is composed four times into each open menu.
Tokens
Every value the component reads, resolved through its aliases to the Foundations primitive.
The shadow is the effect style dropShadow/md: 0 10 15 at minus 3 on black at 5 percent, over 0 4 6 at minus 4 on black at 8 percent. Geometry runs on dimensions/radius/lg 12 for the trigger, dimensions/radius/2xl 24 for the menu and dimensions/radius/xl 18 for the option, with the trigger height on dimensions/spacing/11 44.
Guidelines
Keep it to a handful of options and let the title say what the list is for. Checked marks the current choice, so the menu answers its own question.
Do not use it for a long list. Past about six options on a phone the component's own description sends you to Action Sheet or Picker.
The menu is anchored to its trigger, so it opens where the finger already is. If the thing being chosen has no trigger on screen, that is Only Popover, not a dropdown with an invisible button.