Depending on the typeface, the opening and closing quotation marks may be identical in form (called “vertical” or “straight” or “typewriter” quotation marks), or they may be distinctly left-handed and right-handed (“typographic” or, colloquially, “curly” quotation marks). The closing single quotation mark is identical or similar in form to the apostrophe, and similar to the prime symbol. However, these three characters have quite different purposes. See also: ditto mark.