Apostrophes are used to indicate possession or contraction.


After singular nouns, plural nouns which do not end in s and indefinite pronouns, use ‘s.

For example:

  • Rachel’s laptop
  • Imperial’s new campus
  • Everyone’s responsibility

After plural nouns ending in s, use .

For example:

  • Academics’ workload (the workload of several academics)
  • Volunteers’ t-shirts

When a noun ends with an s and the final syllable is pronounced, use ‘s.

For example:

  • Dr Edwards’s research
  • Thomas’s camera

For compound nouns, and when multiple nouns are linked to make one concept, the apostrophe should be placed at the end of the final part.

For example:

  • the Mayor of London’s proposal


Apostrophes are used to indicate where letters have been omitted. The apostrophe comes in the position where the letters have been omitted, not where the space was between the original words.

For example:

  • Don’t be afraid of Open Source
  • I’ll think about it.

Common mistakes with apostrophes

Apostrophes are often misused. Below are some common mistakes to avoid:

Apostrophes should never be used for a plural noun (unless it is to indicate possession: see above).

For example:

  • The spring flower’s were in bloom
  • Student’s should arrive 20 minutes before the examination begins.

It’s should only be used to signify ‘it is’.

For example:

  • Correct: it’s a beautiful day
  • Incorrect: The fossilised creature carried it’s young in pouches tethered to it’s body

Who’s should not be used to mean ‘whose’

For example:

  • Correct (informal): Who’s attending the dinner?
  • Incorrect: The student, who’s dissertation won an award, graduated in May 2015.

Bullet points

A list of information can be neatly organised using bullet points. How a list is punctuated depends on the sort of information that is being presented.

For a list of short items, there is no need to punctuate each point. A colon should be used to introduce the list, and the first letter of each point should be capitalised.

For example:

Departments in the Faculty of Natural Sciences:

  • Department of Chemistry
  • Department of Life Sciences
  • Department of Mathematics
  • Department of Physics

The Research Office can help with:

  • Preparing a proposal
  • Costing and pricing
  • Managing projects
  • Contracts

For a list of longer items or sentences, which follow on from an introductory sentence, each item should end with a semi colon and the final item should end with a full stop. Ensure that the tense and structure of each item work with the introductory sentence. The first letter of each point should not be capitalised (unless it is a proper noun).

For example:

If you are struggling with any aspect of life at university, remember that you can ask for help from:

  • your tutor, for advice on study techniques, time management, career planning and many other issues;
  • support staff, for guidance on everything from accommodation to library resources;
  • the advice centre run by Imperial College Union;
  • your friends and family.

If a complete sentence introduces the bulleted list, each item in the list should end with a full stop, not a colon, and each point should begin with a capital letter.

For example:

The ‘Study’ section of Imperial’s website suggests free activities in London for students on a budget.

  • Free walking tours are available catering to a range of interests.
  • Free museums include the Science Museum, Victoria & Albert Museum, Natural History Museum, Tate Modern, National Portrait Gallery, British Museum and the Hunterian Museum.
  • Hyde Park and Kensington Gardens are two of the largest parks in London.

Colons and semi 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:
  1. Professional development
  2. Equality and diversity initiatives
  3. 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.


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.

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

For example:

  • Vice-President (Innovation) Professor David Gann attended the event. (No comma after job title)

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:

  • South Kensington accommodation for students includes Southside Halls, Eastside Halls and Beit Hall. No comma needed before the last item in the list.
  • Research themes include Structural biology, Environment and the microbiome, and intelligent use of data. Comma used before last item in list to avoid ambiguity.

Dashes and hyphens

There are three commonly-used dashes, which are distinguishable by their length:

  • The em dash:     —
  • The en dash:      –
  • The hyphen:      -

The em dash should not be used.

The en dash should be used in place of brackets or commas to add supplementary information to a sentence. It should be surrounded by spaces.

For example:

  • The Royal School of Mines – which became part of Imperial College London in 1907 – was established in 1851.

The en dash should also be used for years, to join terms of equal weight, or to represent a pause in the text.

For example:

  • 2015–16 academic year
  • Myers–Briggs profile
  • In May 1851 Hyde Park hosted The Great Exhibition of the Works of Industry of all Nations (or ‘The Great Exhibition’) – the first event of its kind in the world.

A hyphen should be used to join two word adjectives together, and for some words beginning with prefixes such as co, de, pre or re.

For example:

  • First-year students
  • Third- and fourth-year students
  • 19th-century history

Find out more:

For preferred spelling of many commonly hyphenated words, see Appendix 4.

Ellipses and exclamation marks


Ellipses should be used to show that there is some text is missing, for example from a quotation. Ellipses should be surrounded by single spaces. Sentences should not usually finish with an ellipsis.

For example:

  • Dr Paolo Taticchi said: “Imperial College Business School champions the use of innovation and entrepreneurship to address the major challenges facing society … All the students came up with proposals that demonstrate key business skills together with an awareness of the issues facing deprived communities around the world.”

Exclamation marks

Exclamation marks should generally only be used in quotes when writing on behalf of the College. Do not use an exclamation mark coupled with another punctuation mark (for example, do not use !! or !?).

Quotation marks

A colon should be used to introduce a quote.

Double quotation marks should be used for direct quotes.

If a quote appears within a quote, single quotation marks should be used within double quotation marks.

Punctuation marks at the end of quotes should appear within the quotation marks.

For example:

  • One researcher who exhibited her research at the Festival recalled her experience: “The best part for me was seeing members of the public understand what I do. I heard one child say ‘I want to be a biologist!’ as he left our stand: that was hugely rewarding.”

If you break a quote into two paragraphs, omit the closing speech marks at the end of the first paragraph and start the second paragraph with opening speech marks.

For example:

  • Dr Kovac said: “Drones get a bad press but they can improve our lives.

“Aerial robots can help us to monitor pollution and protect wildlife. At Imperial we are working on swarms of aerial robots for future cities.”

Single quotes signify unfamiliar words or phrases.

For example:

  • Approximately 1 in 1,000 people suffer from ‘pathological health anxiety’.


Round brackets

Use round brackets to denote a phrase which adds extra information, a translation, dates, an explanation or definition.

Include full stops, exclamation marks, question marks or quotation marks before the closing bracket only if the complete sentence or quote is in brackets; otherwise, punctuate after the closing bracket.

For example:

  • The show features nearly 50 different devices developed by students on the Innovation Design Engineering (IDE) and Global Innovation Design (GID) courses.
  • Each fellowship will provide up to US$119,000 in support, with an additional supplemental family allowance (approximately $55,000 for partner and two children up to age 18).
  • Taste Imperial is highly committed to sustainable catering. We are proud to support a variety of sustainability pledges and activities. (Please see our sustainable food policy for more information.)

Square brackets

Use square brackets to enclose comments, corrections, references or translations made by a subsequent author or editor.

For example:

  • “If we used all of the 200 million tons [of agricultural waste] available in surplus annually in India, we could meet 17 per cent of the country’s energy needs.”