Punctuation is a set of symbols used in writing to help indicate something about the structure of sentences, or to assist readers in knowing when to change the rhythm or the stress of their speaking. Depending on the style of writing and the language used, punctuation may tend towards one of these purposes more than the other. Common units of punctuation in English and many other languages include the comma, period, apostrophe, quotation mark, question mark, exclamation mark, bracket, dash, hyphen, ellipsis, colon, and semicolon. Each of these units indicates a different thing, and some may have multiple meanings depending on context.
The period or full stop, question mark, exclamation mark, and ellipsis all serve to terminate a sentence. A period is the default terminal punctuation mark, used to end a sentence without conveying any additional meaning. A question mark indicates that the preceding sentence takes the form of an interrogative, and may also be read to change the tone when reading aloud to reflect this. An exclamation mark indicates that the preceding sentence is somehow excited or extremely important, and if read aloud should be given special stress. An ellipsis indicates that some part of the sentence is being omitted; this may be used to refer to a theoretical clause, in which case it usually implies a trailing off of the voice when read aloud, or it may indicate that a real part of the sentence is omitted, often used when quoting long passages or quotations.
The comma is used for a wide range of different purposes in punctuation. In general, it is considered necessary stylistically to have all commas in a sentence serve the same function, to avoid confusion on the part of the reader. A comma may be used to separate units of a sentence such as an introduction or parenthetical thought, to separate items in lists such as this one, to lead a sentence into a quotation, and to separate independent clauses joined by a word such as “and” or “yet”. Commas also have a number of less common uses, too numerous to list in detail.
An apostrophe may be used as punctuation within a word to indicate an omitted letter, as in contractions such as don’t or e’er. It may also be used to show that a noun is possessive, such as in Harry’s name or the Seven Seas’ unrelenting waves.
Quotation marks are used as punctuation to denote quotations within text, or to offset a word or phrase as being an ironic or non-standard usage. The most common type of quotation marks are double quotes, such as: “There is much to like about that,” she said. Or: I wouldn’t say I “missed” work the other day. Single quotation marks, which are a type of punctuation that look similar to an apostrophe, may be used for quotations within quotations, such as in the case of: “As the Bard said, ‘To be or not to be, that is the question,’” He said sagely.
Dashes are used for a number of different purposes, often to link specific things together. A figure dash is used to link numbers together, such as in a phone number. An en dash is used to link things that are within a range, such as page numbers. An em dash is traditionally used to separate a thought from the flow of the sentence – like this – in an almost parenthetical manner. In some modern style guides, the en dash is taking over the em dash’s role of a thought separator in formal writing. A quotation dash is a unit of punctuation which looks approximately the same as the em dash, used to cite a quotation’s source in-text.
Hyphens are punctuation marks which look similar to dashes, but are shorter, and are used to join compound words which haven’t yet become independent words or which are being used adjectivally.
Brackets are used to offset text in some way from the main body. The main type of bracket punctuation used in writing is the parenthesis, with the others being used either to indicate parenthetical thoughts within a set of parenthesis or for specialized usages depending on style.
The colon is a unit of punctuation typically used to introduce a subsequent sentence that is in some way logically linked to the preceding sentence. Therefore, one may find colons serving as punctuation to introduce a list, to offset something that is a consequence of the fact stated in the preceding sentence, or to lead into a quotation.
A semicolon is a unit of punctuation used to link two independent clauses. It is usually used where a period is thought to create too strong a break between the sentences, but a comma is too weak a break. Often, semicolons are also used in place of a comma in lists which use commas for purposes other than offsetting list items, to avoid confusion.