Colons are often used at the end of an independent clause (a complete sentence), giving focus to the words following the colon. Colons have been described as strong pauses, mainly used to indicate that what follows is an illustration or example of what has been referred to before.
According to Silverman, Hughes & Wienbroer (2008), "[c]olons create suspense: they signal that an example, a quotation, or an explanation will follow." They also point out that we cannot use a colon after are, include, and such as. The following situations in which a colon may be used are important to be aware of:
Introducing a list
(1) This essay investigates three aspects of global warming: historical events, environmental influences, and human influences.
As mentioned above, we cannot use a colon after, for instance, are, so the following sentence is not a good alternative:
(2) *This essay investigates three aspects of global warming, which are: historical events, environmental influences, and human influences.
Explaining (or illustrating) the previous statement
(3) The Environmental Management and Policy degree course is highly regarded: academic standards are high, the lecturers cater for on and off campus studies and opens future employment avenues in a variety of fields.
Highlighting a single word
(4) The visiting professor can be summed up in one word: educational.
Preceding a (long) quotation
(5) In view of academic writing being an interactive feat, Hyland (2002, p.1) states the following: "A writer's development of an appropriate relationship with his or her readers is widely seen as central to effective academic persuasion as writers seek to balance claims for the significant, originality, and correctness of their work against the convictions and expectations of their readers."
Introducing an emphatic assertion
(6) This is the bottom line: I refuse to lecture every day.
Between the title and the subtitle
(7) On the Relative Order of Adverbs in the I-domain: A Study of English and Swedish