trace

noun

• An act of tracing.

  "Your cell phone company can put a trace on your line."

• An enquiry sent out for a missing article, such as a letter or an express package.
• A mark left as a sign of passage of a person or animal.
• A residue of some substance or material.

  "There are traces of chocolate around your lips."

• A very small amount.

  "All of our chocolates may contain traces of nuts."

• A current-carrying conductive pathway on a printed circuit board.
• An informal road or prominent path in an arid area.
• One of two straps, chains, or ropes of a harness, extending from the collar or breastplate to a whippletree attached to a vehicle or thing to be drawn; a tug.
• A connecting bar or rod, pivoted at each end to the end of another piece, for transmitting motion, especially from one plane to another; specifically, such a piece in an organ stop action to transmit motion from the trundle to the lever actuating the stop slider.
• (fortification) The ground plan of a work or works.
• The intersection of a plane of projection, or an original plane, with a coordinate plane.
• The sum of the diagonal elements of a square matrix.
• (grammar) An empty category occupying a position in the syntactic structure from which something has been moved, used to explain constructions such as wh-movement and the passive.