★Area

Area is the quantity that expresses the extent of a two-dimensional region, shape, or planar lamina, in the plane. Area plays an important role in modern mathematics.
The SI unit of area is the square metre. Johannes Keppler, who lived from 1571 to 1630, measured the area of sections of the orbits of the planets as they circled the sun using formulas for calculating the area of an oval or circle.