What is ‘shape’?

I just got an email from a fellow photographers daughter who is using one of my artsy fartsy images for a photography class assignment.  How flattering!  Her big question was “Can you define ‘shape’ for me?”  Here’s my answer: To me ‘shape’ is a form that has boundaries or outlines.  You might find geometric shapes like squares or circles; or you might find more organic shapes with less defined edges; or even silhouettes. Shape helps give an image depth.