I'm not a native English speaker and I found in an old book I'm using for research the word "trace" as it follows:
It appears several times in the book, but when I look for its meaning on the Internet, I only found it referred to the trace of a matrix.
Can anyone explain what does it mean?
Best Answer
The trace of a family $\mathscr F$ of subsets of a set $X$ on a subset $A$ is the family$$\{F\cap A\,|\,F\in\mathscr{F}\}.$$