Usually when we say Cylinder we mean a Circular Cylinder, but you can also have Elliptical Cylinders, like this one: You can even have stranger cylinders: if the cross-section is curved and is the same from one end to the other, then it will still be a cylinder.
Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.