This is a pet peeve of mine, as I often hear people use “ex” when they should use “former”. Usually, “ex-“, which is a prefix, is used if the person left the position in question under less than stellar conditions. For example, if a politician has been forced to leave office before the end of his or her term because of some shady or illegal dealings, it would be correct to call that person the “ex-mayor” or “ex-congressman”, etc. Usually, the end of a marriage or relationship is not on such good terms, which is why the person is called your “ex-“.
However, if the person’s tenure is just over, then the proper term should be “former”. “Former” just says that the term or condition is over, period. The situation ended because it was supposed to, not because of any negative circumstances.
Many people use “ex-” and “former” interchangeably; but there really is a difference.
Contact the writing and editing specialists at Writing It Right For You if you have any questions about the correct grammar for your project. We’ll be glad to help!