The place where something begins or ends is called the edge. If you get too close to a cliff’s edge, you might fall off it. Going to the water's edge is not so dangerous.
The part of a knife's blade that actually does the cutting is called the edge. Make sure you keep it sharp! This sense of sharpness is the image you want to have for the many figurative senses of this word. If someone speaks to you with an edge in his or her voice, be careful. They might be getting angry. And if you have an edge over someone, think of yourself as a little sharper because you have the advantage. Your years of training will give you the competitive edge over newcomers to the game. If your company is on the cutting edge of 3D technology, it is the industry leader.