A prism is a solid, three-dimensional figure with the two bases having the same size and shape. Discover how a prism can be defined as a polyhedron with help from a math teacher in this free video on basic math lessons.

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A prism is a solid, three-dimensional figure with the two bases having the same size and shape. Discover how a prism can be defined as a polyhedron with help from a math teacher in this free video on basic math lessons.

Part of the Video Series: Math Lessons

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What is a prism? Hi, my name is Jimmy Chang. I've been teaching college mathematics for nine years, and chances are likely you've seen a prism but you might not have recognized that it actually is a prism. So in the next couple of minutes, we'll be looking at the definition of a prism via certain criteria. So here we go. A prism is a solid three-dimensional figure. By three dimensions, we're talking not the XY axis, two-dimensional figures you've been drawing. So it is a three-dimensional object like a box, but we'll get to that later. In a prism, the two bases or two ends of this figure are going to have the same size and same shape. In other words, the two bases or the two ends of a prism can both be rectangles, triangles, squares, but there is an exception, which we'll get to later on. Also, the two bases and the two ends of a prism are parallel to each other in that they never meet. Each side is a parallelogram, okay? Remember the...what a parallelogram was? At least one pair of...two pairs of parallel sides and two pairs of the equal congruent angles. A prism, though, is a polyhedron, and that has no curved sides -- in other words, all the sides are flat. There are no curves on the side. And last, but not least, because a prism is a three-dimensional figure, we calculate volume. The volume of a prism is the area of the base times the height. So for example, if you have a rectangular prism, otherwise known as a box, you find the area of the base, which tends to be a rectangle or a square, times how tall it is. And if you have a triangular prism, you find the area of the base, which is the triangle -- one-half base times height of the triangle -- and then you multiply it by how tall the prism actually is. So I'm Jimmy Chang, and there you have the definition of a prism.