area
Brahmagupta quadrilateral, a cyclic quadrilateral with integer sides, integer diagonals, and integer area.
Heronian triangle, a triangle with integer sides and integer area.
List of triangle inequalities
One-seventh area triangle, an inner triangle with one-seventh the area of the reference triangle.
Routh's theorem, a generalization of the one-seventh area triangle.
Orders of magnitude—A list of areas by size.
Planimeter, an instrument for measuring small areas, e.g. on maps.
Robbins pentagon, a cyclic pentagon whose side lengths and area are all rational numbers.