Definition of levels:
(adj) :
the same height at all places;
parallel to the ground; at the same height as some reference; constructed as level with
"this table isn't quite level; see how this marble rolls off it?"
(n) :
a tool for finding whether a surface is level, or for creating a horizontal or vertical line of reference; a distance
relative to a given reference elevation
"hand me the level so I can tell if this is correctly installed."
"you can level the table by turning the pads that screw into the feet."