A very small quantity of an element or compound in a given substance, especially when so small that the amount is not quantitatively determined in an analysis; -- hence, in stating an analysis, often contracted to tr.

elements These are chemicals that are needed in small amounts by the aquarium creatures to survive, like vitamins. They must be replenished with food, water changes, or specific additives.

a conceptual connection between two elements or sets of elements that represent a single concept at different semantic levels or from different points of view

A dependency that indicates a historical or process relationship between two elements that represent the same concept without specific rules for deriving one from the other.

the sum of the main diagonal elements of a square matrix. See main diagonal.

In linear algebra, the trace of an n-by-n square matrix A is defined to be the sum of the elements on the main diagonal (the diagonal from the upper left to the lower right) of A, i.e.,