Principle Of Closure
The Principle of Closure refers to the belief held in the Gestalt school of psychology that the human brain is inclined to perceive forms and figures in their entirely and complete appearance in spite of the absence of one or more parts, whether they are absent or hidden. This is one of the 5 Gestalt principles of grouping.
For instance, if you are looking at a tree in the distance, but can only see top half, your brain is able to visualize the entire tree. Or in the image below you perceive a circle and a square even though some of the pieces are missing. https://upload.wikimedia.org/wikipedia/commons/thumb/3/30/Gestalt_closure.svg/220px-Gestalt_closure.svg.png