Floor

Floor[x] gives the greatest integer less than or equal to x.

Floor[x, a] gives the greatest multiple of a less than or equal to x.

Examples

Floor of a number:

Floor[3.7]
(* 3 *)

Floor[-2.3]
(* -3 *)

Floor to a multiple:

Floor[17, 5]
(* 15 *)

Please visit the official Wolfram Language Reference for more details.