stairway
n.a set of steps that you use to go from one floor of a building to another. It is usually inside a house or an office.
n.a set of steps, including the supporting structure and handrails, providing access between different levels of a building.
“The wooden stairway leads to the second floor.”
“The architect designed a wide, spiral stairway to serve as the central feature of the hotel lobby.”
“Emergency protocols require that the stairway remain clear of obstructions at all times to ensure a rapid evacuation during a fire or other building crisis.”
Often used interchangeably with 'staircase', though 'stairway' more frequently refers to the entire passage or route.
stair + way
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.