colon

colon

1. The colon is the punctuation mark that is least used and least well understood in ordinary writing (as distinct from printing). The principal difference between it and the semicolon lies in the relation of what precedes and follows each in the sentence. A semicolon links two balanced or complementary statements, whereas a colon leads from the first statement to the second, typically from general or introductory statement to example, from cause to effect, or from premiss to conclusion.

2. The respective roles of semicolon and colon are shown by the following example punctuated in two ways: It was a beautiful day; we played cricket on the green / It was a beautiful day: we played cricket on the green. In the first version, the two statements about the weather and playing cricket are equally balanced and might alternatively be separated by and or written as two distinct sentences separated by a full stop. In the second version, the colon makes the second statement much more explicitly a consequence of the first.

3. A colon is also used to introduce a list: The following will be needed: a pen, pencil, rubber, and ruler. Note that the colon should not be followed by a dash, although this practice is more common in older printing.

4. In AmE, a colon follows the initial greeting in a letter (Dear Ms Jones:), but in BrE a comma is customary. A colon also separates hours and minutes in notation of time in AmE (10:30 a.m.).