Number theory was famously described as absolutely, gloriously useless by G H Hardy, but is now vital for encryption and therefore the digital economy (and all else “e”) While looking this up, I came across this discussion on the site Math Overflow. And in that discussion, I came across this comment:
Pet peeve: “cf” stands for “conferre”, which means “to compare”; you are using it as reference or a “see for example”. Though an extremely common usage, it is incorrect. “cf” should be used for “compare with”, and you don’t want to compare the writings of Hardy with the statement that Number Theory was considered useless; rather, you want to use Hardy’s writings as a reference to the assertion that Number Theory was considered useless…
The abbreviation cf. (short for the Latin: confer/conferatur, both meaning “compare”) is used in writing to refer the reader to other material to make a comparison with the topic being discussed. It is used to form a contrast, for example: “Abbott (2010) found supportive results in her memory experiment, unlike those of previous work (cf. Zeller & Williams, 2007).” It is recommended that “cf.” be used only to suggest a comparison, and the word “see” be used to point to a source of information.
I am ashamed to say that for my whole life (well, the portion of my life I have used Cf., which I would say is twenty-something years) I has been offedning Arturo Magidin and indeed proper usage by using it to mean “See”.
You learn something new every day.