a small quantity; or any indication or evidence of
The exact meaning of this sense of trace depends upon its context. For example:
a small indication that something was present — as in "The plane disappeared somewhere over the Pacific Ocean without leaving a trace."
a very small amount of something — as in "The blood test showed a trace of steroids."
any evidence of something — as in "We did not find a trace of the gene."
September had come, but not a trace of cool weather with it, and we were still sleeping on the back screen porch.
trace = slight indication or sign
Other Uses (with this meaning)
Farther down stream, beyond the bluff, were traces of an old cotton landing, where Finch Negroes had loaded bales and produce, unloaded blocks of ice, flour and sugar, farm equipment, and feminine apparel.
traces = indications
We saw no trace of Tim Johnson.
trace = indication
There are no more uses of "trace" flagged with this meaning in To Kill a Mockingbird.