Semicolon

The semicolon or semi-colon (;) is a punctuation mark that separates major sentence elements. A semicolon can be used between two closely related independent clauses, provided they are not already joined by a coordinating conjunction. Semicolons can also be used in place of commas to separate the items in a list, particularly when the elements of that list contain commas.

Although terminal marks (i.e. full stops, exclamation marks, and question marks) mark the end of a sentence, the comma, semicolon and colon are normally sentence-internal, making them secondary boundary marks. The semicolon falls between terminal marks and the comma; its strength is equal to that of the colon.

Constraints

1. When a semicolon marks the left boundary of a constituent (e.g., the beginning of a clause or a phrase), the right boundary is marked by punctuation of equal or greater strength.
2. When two or more semicolons are used within a single construction, all constituents are at the same level, unlike commas, which can separate, for example, subordinate clauses from main clauses.

Usage

Semicolons are followed by a lower case letter, unless that letter would ordinarily be capitalized mid-sentence (e.g., the word "I", acronyms/initialisms, or proper nouns). Modern style guides recommend no space before them and one space after. They also typically recommend placing semicolons outside ending quotation marks, although this was not always the case. For example, the first edition of the Chicago Manual of Style (1906) recommended placing the semicolon inside ending quotation marks.

Applications of the semicolon in English include:

• Between items in a series or listing containing internal punctuation, especially parenthetic commas, where the semicolons function as serial commas:
  • The people present were Jamie, a man from New Zealand; John, the milkman's son; and George, a gaunt kind of man with no friends.
  • Several fast food restaurants can be found within the following cities: London, England; Paris, France; Dublin, Ireland; Madrid, Spain. Here are three examples of familiar sequences: one, two, and three; a, b, and c; first, second, and third.
  • (Fig. 8; see also plates in Harley 1941, 1950; Schwab 1947).
• Between closely related independent clauses not conjoined with a coordinating conjunction, when the two clauses are balanced, opposed or contradictory:
  • My wife would like tea; I would prefer coffee.
  • I went to the basketball court; I was told it was closed for cleaning.
  • I told Kate she's running for the hills; I wonder if she knew I was joking.
    Either clause may include commas; this is especially common when parallel wording is omitted from the second:
  • Ted has two dogs; Sam, one.
• When a comma replaces a period (full stop) in a quotation, or when a quotation otherwise links two independent sentences:
  • "I have no use for this," he said; "you are welcome to it."
  • "Is this your book?" she asked; "I found it on the floor."