Punctuation marks function as a way for writers to imitate the stops, pauses and inflections naturally present in speech. For example, the question mark indicates the rising inflection used by speakers to ask a question, while the period indicates the pause that typically occurs between separate thoughts. Punctuation marks originated among ancient orators, who marked the best placement and length for pauses on copies of their speeches.
Common punctuation marks include the comma, which indicates a shorter pause than the period, and the exclamation mark, which indicates strong feeling. Other punctuation marks include apostrophes, used to indicate ownership or omitted letters, and quotation marks, used to indicate words said by someone else.
Rules for using punctuation marks change over time. Many people do not follow traditional punctuation rules when text messaging for fear of appearing too formal. Senders of text messages frequently omit periods and commas altogether or use multiple exclamation points or question marks at the end of sentences.
As of 2015, several punctuation marks are obsolete, including the interrobang, which combined the exclamation point and question mark and made a short appearance in the 1960s, and the percontation mark, used briefly in the late 16th century to indicate rhetorical questions.