Hectare (ha)
The hectare, or ha, is a metric area unit equal to 10,000 square meters (a square with 100-meter sides). First used in France in 1795, it is now widely used worldwide, particularly in farming, forestry, and land planning. Although it is not an official SI unit, it is permitted because it is practical for measuring fields and properties. Its simple size makes it better than the square kilometer for medium areas.
Square Inch (in²)
The square inch, or in², is the smallest commonly used unit of area in the imperial system. It is the area of a square with one-inch sides and equals 6.4516 square centimeters. It originates from the inch and has been widely used in engineering, technical drawings, and manufacturing. Today, it is still good for small things like screens, machine parts, and prints. Most countries now use square centimeters, but the square inch is still used in areas where the imperial system is prevalent.