EoA: Form

Form is the outline of any object or set of objects.  So, if you saw something you'd normally recognize, like in this image:

You know that it's a ballet dancer, by the outline or form of the shape.  You don't know what her race is, nor do you know what color her dress is, but you know she's a ballet dancer just by her form.

Resources:

http://www.williamsclass.com/ElectiveClassArt/ArtElementNotes.htm