An airplane is defined as:

An airplane is characterized as an engine-driven, fixed-wing aircraft that is heavier than air. This definition emphasizes several key aspects that distinguish airplanes from other types of aircraft.

First, the term "engine-driven" indicates that airplanes typically rely on engines for thrust, which enables them to achieve and sustain flight. They are designed to create lift through their fixed wings, which do not move or rotate like those on rotorcraft.

Second, being "fixed-wing" means that the wings are stationary and are not capable of changing positions to generate lift; they remain in a fixed location relative to the fuselage of the aircraft. This feature is crucial for the aerodynamic principles that enable airplanes to fly.

Lastly, the phrase "heavier than air" differentiates airplanes from lighter-than-air vehicles like balloons or airships, which use buoyancy to ascend and remain airborne without the need for engine power.

This comprehensive definition encapsulates the fundamental characteristics of airplanes and distinguishes them clearly from other flying vehicles, thus confirming that this option accurately describes what an airplane is.