A stair is ane step in a flicht o stairs. An aa called a stairstep. [1]

Stairway o the Opéra Garnier (Paris, Fraunce)

References

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  1. R. E. Putnam and G. E. Carlson, Architectural and Building Trades Dictionary; 3rd edition, American Technical Publishers, Inc., 1974, ISBN 0-8269-0402-5