A mark of omission is a symbol used to indicate that something has been removed or omitted from a text. The two most common marks of omission are the DELE, which is a four-letter symbol that looks like a backwards 'D', and the CARET, which is a five-letter symbol that looks like an upside-down 'V'. Both of these symbols are used to indicate that something has been removed from a text, usually for the purpose of editing or correcting it.