A monoplane is an airplane with a single set of wings. The word comes from mono, meaning “one,” and plane, short for airplane. Most modern aircraft are monoplanes: passenger jets, fighter planes, and small private aircraft all have just one pair of wings attached to the fuselage (the main body of the plane).

This might seem obvious today, but early aviation pioneers experimented with many wing configurations. Biplanes had two sets of wings stacked on top of each other, and triplanes had three. These multiple wings provided more lift and strength with the lightweight materials and weak engines available in the early 1900s. The famous Wright brothers' first airplane was a biplane, as were many World War I fighters like the Sopwith Camel.

As engineers developed stronger materials and more powerful engines, the monoplane design proved superior. A single wing creates less air resistance (called drag) than multiple wings, allowing planes to fly faster and more efficiently. By World War II, monoplanes had largely replaced biplanes for military and commercial aviation. When you see a plane flying overhead today, you're almost certainly looking at a monoplane, the design that won out through a century of aviation innovation.