Definition
Aircraft with two main wings stacked one above the other, typically connected by struts and bracing wires. The two-wing arrangement provides a large total lifting surface within a short wingspan, at the cost of additional drag from the structure between the wings.
Plain English
Airplanes that have two wings on top of each other instead of just one. The double wing gives plenty of lift in a compact frame, but the extra structure slows the aircraft down.
Context Anchor
Seen in discussions of wing design, older aircraft, aerobatic aircraft, and aircraft recognition.
Derivation
From the Latin 'bi-' meaning 'two' and 'planum' meaning 'flat surface' — literally 'two flat surfaces.' Early aviation used 'plane' to mean a wing (a flat lifting surface), so a biplane is simply an aircraft with two wings.
Why Pilots Care
Biplanes usually have more drag than single-wing aircraft, so they often fly slower for the same engine power. Recognizing the design helps a pilot understand basic performance and handling differences.
Intuition Check
Do not read “biplane” as two airplanes. It means one airplane with two main wings stacked vertically.
Example Sentence 1
Many early aircraft, including the Wright Flyer, were biplanes because the second wing added lift without requiring a longer wingspan.
Example Sentence 2
Some training aircraft still use biplane designs for their stability at low speeds.