On a fixed-wing aircraft, the span or straight-line distance between one wingtip and the other, including any projecting ailerons. (The term "wingspan" always refers to the tip-to-tip span of an entire wing; never to a wing half on just one side of a fuselage.)
linear distance between the extremities of an airfoil
The distance from one wingtip to the other.
The length of the wing, as measured from one wing tip to the other.
Wingspan is the distance measured across a butterfly's (or moth's) wings.
The wingspan (or just span) of an airplane is the distance from the left wingtip to the right wingtip. For example, the Boeing 777 has a wingspan of about 60 m (200 feet).