Short for compare — the mark that sends a reader elsewhere. A named abbreviation rather than a concept.
Latin confer, the imperative of conferre (to bring together, to compare), from com- (together) + ferre (to carry); used in print since the early modern period to send a reader to set one passage beside another.
Short for 'compare' — the mark that sends a reader elsewhere to set two things side by side before judging either alone.