On Composition series before, we've talk about line Composition Element as the one of composition elements in photograph. now, we will talk about next elements which is : Form

Basically, characteristic of Shape is more fundamental better than the other elements because shape is our way for identification toward an object. You can predict about how the face of radio broadcaster from the voice that you listen, but without looking the face directly. Maybe you smell the flower and guess the flower type, but without looking the shape directly and you never sure your guess is right or wrong. 

Basically, form give your photo an obvious identity so people who look is no need to guess. A silhouette photo like the photo above is the most real example about shape.

For more clear implementation, geometry shape also can be used as the standard to set some objects in your photo, so your photo will looks more dynamic and orderly at once. For example you have to shoot 3 people at once in a photo, if you set all of them to stand in same high , you will get a awkward photo. It's different if you set them to form a triangle so photo overall will looks more dynamic, balanced, and interesting.