A switchback stair reverses 180° with two parallel flights and an intermediate landing. Common in commercial and exterior settings.
A switchback (or scissor) stair runs up one flight, turns 180 degrees at a landing, and continues up a parallel flight in the opposite direction. Structurally it is identical to a U-shaped / half-turn stair; "switchback" is the term favoured for commercial egress and exterior hillside stairs.
Yes, structurally. A switchback reverses direction 180 degrees with parallel flights.
Commercial egress stairwells, parking structures, and hillside or landscape stairs.
Yes. The 180° reversal happens at an intermediate landing.