The Colon ( : )

The colon is used to introduce a specification or a quotation.

Colon for specification

The colon introduces a specification in the form of examples, definitions or extra information concerning something previously mentioned in the same sentence. It carries the reader from the general to the particular, from the vague to the precise, from the abstract to the concrete.

• That’s all gravity is: the distortion of the space-time fabric, affecting how things move .
• The reason patterns often appear in nature is simple: The same basic physical or chemical processes occur in many patterned substances and organisms as they form .
• To sum up: research suggest it’s probably fine to listen to music while you’re studying - with some caveats .

Colon for introducing reported speech or a quotation

• We could open an envelope asking the question: “Are you a green or a red card?” .
• A classic quote (attributed to physicist Richard Feynman, but in this form also paraphrasing Niels Bohr) surmises: “If you think you understand quantum mechanics, you don’t understand it.”

Colon for introducing a list

Formatted lists are often introduced by a colon:

• To sum up: research suggest it’s probably fine to listen to music while you’re studying - with some caveats. It’s better if:
  • it puts you in a good mood;
  • it’s not too fast or too loud;
  • it’s less wordy (and hip-hop, where the words are rapped rather than sung, is likely to be even more distracting);
  • you’re not too introverted.

Test your understanding of colon punctuation with the Colon/Semicolon Punctuation Quiz.