Colons and Semi-colons: a Guide

A lot of students get confused by colons and semi-colons. Some sprinkle them randomly in a text and hope. Some never use them, in fear. Some put semi-colons everywhere in the misplaced conviction that just using them at all is a good thing. All this is understandable. I was never taught how and when to use one, and even if you were, you may not have absorbed it.

Colons and semi-colons are just a part of the punctuation minefield of essay writing, but they are a particularly problematic part, and I thought you might find a straightforward guide with some clear rules helpful. This document contains some grammatical jargon, but these terms are explained, hopefully providing a balance between precision and clarity.

When to use a semi-colon

  1. To join independent clauses in a compound sentence. An independent clause is one that could stand alone as its own sentence; hence, the new sentence is said to be a ‘compound’ sentence, because it combines two or more sentences. These clauses are joined because the writer thinks they bare a close relation, or wishes to indicate a closer relation than a new sentence would indicate. The semi-colon in this case replaces a conjunction (and, but, or, etc.):
  2. ‘It was the end of term; Ro had a mountain of marking to do.’
  3. To join complex independent clauses in a compound sentence via a conjunctive verb (however, hence, meanwhile, moreover etc.):
  4. ‘It was the end of term, and for her students, the work was done; however, for Ro the work had just begun.’
  5. To separate a list whose items are complicated by commas:
  6. ‘Walter loved everything about her: her deep, brown eyes; her long, red hair; but most of all, her mind, and her refreshingly radical opinions.’
  7. In a complex sentence, where to use a comma might be confusing. For example, take this sentence:
  8. ‘For this exercise, Alice will work with Brad, and Catherine and Derek will work with Elizabeth’
  9. This is potentially confusing. Who is Catherine working with? So instead you could write:
  10. ‘For this exercise, Alice will work with Brad; and Catherine and Derek will work with Elizabeth’
  11. A comma isn’t strictly wrong, here, but the semi-colon does make things clearer

When to use a colon

  1. After an independent clause, in order to introduce a list:
  • ‘We will be looking at three philosophers this week: Descartes, Berkeley, and Hume.’
  1. To introduce an explanation or example that clarifies or impacts on the clause that precedes it:
  • ‘All things considered, there was really only one thing she could do: finish the blasted essay.’
  • Note that colons are often used in this way if a quotation explains or gives an example for the clause that precedes it (although one can also use commas before quotations if the quotation serves some other purpose)

Semi-colons and colons do not indicate the end or beginning of a sentence, they replace them. Therefore, you should not have a capital letter following a colon or semi-colon. (Note that quotations may be excluded from this rule. Your quotation should accurately reflect the original text. If it is the start of a sentence, it should have a capital letter.)