Plain English Meaning

Airfoils are the specially shaped parts of an airplane — like the wings and propeller blades — that create lift when air flows over them. Their curved shape is what lets the airplane fly.

Full Definition

Airfoils are shaped surfaces — such as wings, propeller blades, and control surfaces — designed to produce a useful aerodynamic force (primarily lift) as air flows around them. Their cross-sectional shape, with a curved upper surface and flatter lower surface, causes air to flow at different speeds and pressures above and below, generating lift when the airfoil moves through the air at a suitable angle.

Context Anchor

Seen in discussions of how wings, tail surfaces, and propellers work as the airplane moves through the air.

Derivation

From 'air' plus ',' an old word for a sheet or leaf-like shape (from the Latin 'folium,' meaning leaf). So an airfoil is literally a 'leaf-shaped object designed to work in the air.' That image — a 's cross-section really does look like a thin, curved leaf.