stairs
Flight of stairs and Fleet of ships.
stairs
A group of stairs is referred to as a flight. Example in a sentence- I followed him up a flight of stairs.
volley of savages string of pearls flight of stairs cache of arms
They're not called stairs. They're called steps. Stairs are indoors. Steps are out doors.
Flight
It is called a stile.
Risers.
Along the stairs that run along group 13 to group 17
They could be known as either a stairway, staircase, stairwell, or a flight of stairs.
The hospital where Hazel Grace went in "The Fault in Our Stars" is called the Cancer Support Group. It is not a conventional hospital but a support group where cancer patients gather to share their experiences.