Two numbers, x and y: one value, or a field that changes from point to point.
When a 2D Vector varies over space.
The in-plane length of the vector at each point.
The field pointing the opposite way.
The field scaled to length 1 at each point; where it is zero it stays zero.
The field's x component.
The field's y component.
Items that are each a 2D Vector. One 2D Vector wired where a list is taken counts as a list of one. A list wired where one 2D Vector is taken runs the block once per item.