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, Comma

Commas create pauses in a sentence, but you can't put them just anywhere (sometimes people dot them around, rather than placing them carefully). Where you put a comma changes the meaning.

To help you see where you need pauses, try reading your piece of work aloud.

Example

This has no commas. Try reading it without pauses. You will be out of breath. It is confusing.
*Many students are part-time or distance learners in full-time employment and the distinction between full and part-time students is less clear with people coming in and out of employment and returning to university several times during their lives.

This is the same passage, with commas. It now makes more sense, and is more interesting.
Many students are part-time or distance learners, in full-time employment, and the distinction between full and part-time students is less clear, with people coming in and out of employment and returning to university several times during their lives.

You can also use a colon (:) or semicolon (;) to make pauses. Use the menu to go to Advice about them. The following gives four main uses of the comma. Further advice and descriptions of use are available in the Development Level of Writing for University Courses.

To show where two parts of a sentence are linked

Commas often come before a word which links two parts of the sentence, like
and
but
so
or

You do not always need a comma before such words. If your sentence is very short you may not need one.

Examples

In this short sentence a comma is not needed.
A beautiful garden is pleasant but making it look beautiful is hard work.

This sentence is long and needs a comma, because you need a pause.
It is very pleasant to sit and while away the hours in a beautiful garden, but it is less pleasant to do the hard work which makes it beautiful.

To separate off a section of a sentence

Where a section of a sentence is not essential but adds something to it, you separate it off by putting commas around it.

Example

Many students are part-time or distance learners, in full-time employment, and the distinction between full and part-time is blurring.

The sentence would stand alone without the underlined words - they give more information about the part-time and distance learners.

To show which groups of words in a sentence belong together

Most sentences, especially longer ones, have two or more groups of words which belong together.

Commas can show where the groups of words start and end, and which group belongs to what. Changing the position of the comma changes this and can therefore change the meaning - so it is very important to place commas correctly.

Examples

Many students are part-time or distance learners, in full-time work, and the distinction between full and part-time is no longer clear.

Many students are part-time, or distance learners in full-time work, and the distinction between full and part-time is no longer clear.

In the first example the underlined words belong to part-time or distance learners i.e. many of both sorts of students are in full-time employment. The commas around in full-time work create this effect.

In the second example there is a comma after part-time and no comma after distance learners. This means in full-time work belongs only to distance learners, i.e. many distance learners are in full-time employment (but not part-timers).

It really helps in seeing how to use commas if you know more about groups of words in sentences and how they relate to each other. See Making longer sentences in the Main Rules of Written English topic at Development Level.

In a list
In a list you can either :
  • use a comma between each item and have a joining word between the last two items (e.g. and, or), instead of the final comma
  • or put a colon (:) before the list starts and a semicolon (;) between each item. You do not have a joining word between the last two items.
Examples

These are both correct.
It helps if a town with a large university has good accommodation, sporting facilities, places of worship for different religions, shops, banks, theatres, art galleries, cinemas, bars, cafes and clubs.

It helps if a town with a large university has: good accommodation; sporting facilities; places of worship for different religions; shop; banks; theatres; art galleries; cinemas; bars; cafes; clubs.

You also use commas between adjectives listed before a noun (there should be no comma between the last adjective in the list and the noun). The commas create pauses and show that all the words belong to the noun.

Example

It was a big, black, fast car.

In a list of references

There are accepted conventions about where you put commas in the items in a list of references. Their main use here is to separate off items in the reference.

In the following example, a comma is used between the names of the two authors to separate them.

Example

DREW, S., BINGHAM, R. (2001). The student skills guide. Gower.

For details of other resources which give advice on referencing, see References and Resources in the Main Menu.

© Learning & Teaching Institute, Sheffield Hallam University 2004