The colon (:)
The colon is now seldom used but is necessary:
1. to instruct an enumeration (naming one by one)
e.g. send me the following articles: a pen, a ruler, a brush and some writing paper.
2. to introduce a speech or quotation beginning with the words like “thus”, ‘as follows”
e.g. The poet Keats wrote of Autumn thus: “Season of mists !”
3. to introduce long quotations
e.g. The following are the chief cities: London, Paris, Moscow, New York, Bombay.