1.
a. A visible mark, such as a footprint, made or left by the passage of a person, animal, or thing.
b. Evidence or an indication of the former presence or existence of something; a vestige.
2. A barely perceivable indication; a touch: spoke with a trace of sarcasm.
3.
a. An extremely small amount.
b. A constituent, such as a chemical compound or element, present in quantities less than a standard limit.
4. A path or trail that has been beaten out by the passage of animals or people.
5. A way or route followed.
6. A line drawn by a recording instrument, such as a cardiograph.
7. Mathematics
a. The point at which a line, or the curve in which a surface, intersects a coordinate plane.
b. The sum of the elements of the principal diagonal of a matrix.
8. An engram.
(from the Free Online Dictionary)
