Definition
Curved inward, like the inside of a bowl. In airfoil design, a concave surface curves away from the oncoming airflow, forming a hollow rather than a bulge.
Plain English
Curving inward. The surface dips in, the way the inside of a spoon does.
Context Anchor
Seen in airfoil shape discussions when describing the curved surfaces of a wing cross-section.
Derivation
From Latin concavus, meaning 'hollow' or 'arched inward.' The 'cav' part is the same root as 'cave' — a hollowed-out space. That image of a hollow curve is exactly what concave means in airfoil shape.
Why Pilots Care
Concave lower surfaces on airfoils can increase lift at low speeds but may alter stall behavior and drag.
Intuition Check
Concave does not mean simply curved. It means curved inward or hollowed, not curved outward.
Example Sentence 1
The lower surface of some highly cambered wings is slightly concave to increase lift at low speeds.
Example Sentence 2
The student pilot noted how the concave camber changed the airfoil’s stall characteristics.