Definitions of linear:

• adjective:   designating or involving an equation whose terms are of the first degree
• adjective:   measured lengthwise
• adjective:   of a leaf shape; long and narrow
• adjective:   of or in or along or relating to a line; involving a single dimension

  Example: "A linear foot"

• adjective:   of a circuit or device having an output that is proportional to the input

  Example: "Linear amplifier"

• name:  A surname (very rare: popularity rank in the U.S.: #31625)