- commaThere is much variation in the use of the comma in print and in everyday writing. Essentially, its role is to give detail to the structure of sentences, especially longer ones, and to make their meaning clear by marking off words that either do or do not belong together. It usually represents the natural breaks and pauses that occur in speech. The principal uses are as follows:1. To separate adjectives coming before a noun: a cold, damp, badly heated room / a ruthless, manipulative person. The comma can be replaced by and between a pair of adjectives to make a stronger effect: a ruthless and manipulative person. The comma is omitted when the last adjective has a closer relation to the noun: a distinguished foreign politician / a dear little baby.2. To separate the main clauses of a compound sentence when they are not sufficiently close in meaning or content to form a continuous unpunctuated sentence, and are not distinct enough to warrant a semicolon. A conjunction such as and, but, yet, etc., is normally used: The road runs close to the coast, and the railway line follows it closely. It is incorrect to join the clauses of a compound sentence without a conjunction (the so-called ‘comma splice’): ☒ I like swimming very much, I go to the pool every day. (In this sentence, the comma should either be replaced by a semicolon, or retained and followed by and.) It is also incorrect to separate a subject from its verb with a comma: ☒ Those with the lowest incomes and no other means, should get the most support. (Remove the comma.)3. A comma also separates complementary parts of a sentence, and can introduce direct speech: Parliament is not dissolved, only prorogued / The question is, can this be done? / He then asked, ‘Do you want to come?’.4. An important function of the comma is to prevent ambiguity or (momentary) misunderstanding: In the valley below, the houses look very small (The valley is not below the houses) / Mr Hogg said that he had shot, himself, as a small boy (Mr Hogg shot things other than himself).5. Commas are used in pairs to separate elements in a sentence that are not part of the main statement: There is no sense, as far as I can see, in this suggestion / It appears, however, that we were wrong / There were, to be sure, at least four pubs in the village. They are also used to separate a relative clause from its antecedent when the clause is not a restrictive or identifying one (see clauses): The book, which was on the table, was a gift. (Without the comma, the relative clause would serve to identify the book in question rather than give extra information about it: The book which/that was on the table was a gift). A single comma usually follows adverbs (such as already, however, moreover) in initial position in a sentence: Already, the sun was shining / Moreover, you were late home from school.6. Commas are used to separate items in a list or sequence. Usage varies as to the inclusion of a comma before and in the last item; the style recommended here is to include it (the so-called ‘Oxford comma’): We ordered tea, scones, and cake. Other practice is to include it only to avoid ambiguity: We ordered tea, bread and butter, and cake.7. Omit the comma between nouns in apposition (e.g. my friend judge Leonard / her daughter Mary), but retain it when the noun is a parenthesis (e.g. His father, Humphrey V. Roe, was not so fortunate).8. Commas are used in numbers of four or more figures, to separate each group of three consecutive figures starting from the right (e.g. 14,236,681). Omit the comma when giving house numbers in addresses (44 High Street), and in dates (27 July 2001).
Modern English usage. 2014.