Commas, colons and semi colons

Commas

Pairs of commas should be used to surround non-defining words, phrases or clauses (which add descriptive information, but can be removed without losing the meaning of the sentence).

For example:

  • The car, which was built in France in 1900, formed part of the Transport Zone at the 2016 Imperial Festival.
  • Imperial’s President, Professor Alice P. Gast, welcomed former students to the Alumni Weekend.
  • It was, however, too late to register.

Common mistakes with commas

Commas should not be used when defining information appears at the start of a sentence.

For example:

  • Incorrect: Vice-President (Innovation), Professor David Gann attended the event.
  • Correct: Vice-President (Innovation) Professor David Gann attended the event.

Commas should not be used to join two main clauses: either a semi colon or a coordinating conjunction (such as and, but, or so) should be used instead.

For example:

  • Incorrect: Bioengineering graduates are highly sought after, they go on to careers in the industrial, commercial and consulting sectors.
  • Correct: Bioengineering graduates are highly sought after, and they go on to careers in the industrial, commercial and consulting sectors.

Do not include a comma before the last item in a series of items, sometimes known as an Oxford comma, unless it aids comprehension.

For example, a comma is not needed before the last item in this list:

  • South Kensington accommodation for students includes Southside Halls, Eastside Halls and Beit Hall.

For example, a comma is used here before the last item in in list to avoid ambiguity:

  • Research themes include Structural biology, Environment and the microbiome, and intelligent use of data. 

Colons

Use a colon to introduce lists, presented either in prose or using bullet points. In prose, the colon should be followed by a single space. The first word after the colon should not be capitalised unless it is a proper noun.

For example:

The Outreach office organises mentoring and tutoring for secondary school pupils, including: the INSPIRE teacher training scheme; Schools Plus tutoring; Outreach Postgraduate Ambassadors; and IntoUniversity mentoring.

Your Human Resources contact can help with queries relating to:

  • Professional development
  • Equality and diversity initiatives
  • Pay and benefits

Semi colons

A semi colon can be used to link two related parts of a sentence, as long as those parts could stand alone as a complete sentence.

For example:

  • The Imperial Festival returns this year on 7 May; last year the College welcomed over 12,000 visitors to the event.

Semi colons should also be used instead of commas in a complicated list or sentence, to improve clarity and understanding.

For example:

  • Imperial’s Strategy 2015–2020 outlines how the College intends to achieve its mission. It emphasises the importance of maintaining world class core academic disciplines; encouraging multidisciplinary research, especially that which addresses global challenges; and embedding the educational experience of students in a vibrant, research-led, entrepreneurial environment.