concept

Induced drag

The part of a wing's drag that is the price of making lift at all. A wing holds a body up by throwing air downward - but that downward-moving air also tilts the oncoming flow, so the lift vector leans slightly backwards, and that rearward lean is induced drag. It scales with the square of the lift and inversely with the square of the span, which is why long wings are cheap: it is the reason an albatross has a narrow, very long wing, and the reason two short wings stacked one behind the other can never match a single long wing of the same total area.