The question mark (?), also known as an interrogation point, question point, query,or eroteme, is a punctuation mark that replaces the period at the end of an interrogative sentence. It can also be used mid-sentence to mark a merely interrogative phrase, where it functions similarly to a comma, such as in the single sentence "Where shall we go? and what shall we do?", but this usage is increasingly rare. The question mark is not used for indirect questions. The question mark character is also often used in place of missing or unknown data.