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The amount of space within the boundaries of a two-dimensional shape, reported in square units (like miles2 or feet2). Area is essentially space, but don't go around saying things like, "area-ships," "area cadets," or the area-bar.

Area Addition Postulate

The assumption that we can add areas together. This is what allows us to find the areas of weird-looking polygons by breaking them up into simpler ones. The total area is equal to the sum of its individual parts. Just make sure the parts don't overlap or leave any gaps.


One of the sides of a polygon that we use to calculate area. We choose bases based on the type of shape we're dealing with.


The straight perpendicular line from the base to the top most point of a shape (either a side or a vertex) down to the base. Remember, the base may need to be extended to find the height.


A "slice" of a circle whose area can be calculated if the radius r and central angle θ is known.
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