Ex can refer to various things.

• ex (editor), short for EXtended, is a line editor developed for the UNIX operating system.

• In English, ex is the word for the letter "x" or "X".
• In typesetting, an "ex (typography)" refers to the height of the lowercase letter "x" in a given font.
• In Latin, ex means "out of"

• In social relationships, an ex (relationship) is someone with whom a person was once associated, often romantically.
• As a prefix, ex generally denotes the former state of something.
• In the context of current French politics, the Ex is Valéry Giscard d'Estaing, former president.