How does one use the Latin word "cum" in a sentence?
Solution 1:
Cum is the Latin word for with and is usually used to join two nouns, showing that something serves two purposes.
She is a waitress-cum-singer in the restaurant.
This is my bedroom-cum-study.
Solution 2:
About that matter, Etymonline says of the use of the Latin cum preposition:
The sexual cum seems to have no connection with Latin cum, the preposition meaning “with, together with”, which is occasionally used in English in local names of combined parishes or benifices (e.g. Chorlton-cum-Hardy), in popular Latin phrases (e.g. cum laude), or as a combining word to indicate a dual nature or function (e.g. slumber party-cum-bloodbath).
It's to be noted that both have the same pronunciation (/kʌm/ in British English, /kəm/ in American English). Both Etymonline, the New Oxford American Dictionary and Cambridge Advanced Learner’s Dictionary have it written “X-cum-Y”, with hyphens. Funnily, the later two use related examples, NOAD going for “study-cum-bedroom” and Cambridge for “bedroom-cum-study”.
However, modern usage doesn't always follow that prescription, at least in American English. The Corpus of Contemporary American English data for 2010 shows 11 occurrences using hyphens, and 3 occurrences without hyphens (such as “lawyer cum fitness enthusiast”, right there).
Solution 3:
The word cum is Latin for 'with', as in cum laude, which means "with honour". It is used in Latin Honors, as in
magna cum laude -- with great honour.
or
summa cum laude -- with highest honour.
As Jasper said, it is used in English to connect to things that are closely related.
Solution 4:
It also means "when" when it is presence of a subjunctive e.g. cum portavisset - "When he had carried"