Separating the parts of a sentence

Commas are used to separate an introductory word or phrase from the main sentence, or to separate a word or phrase that briefly interrupts the flow of the sentence. In the examples below, the introductory and interrupting words or phrases have been italicised.

Nevertheless, many critics see value in this theory.

After the first decade, the changes were fully integrated into the system.

Numerous studies, however, prove that the theory is inaccurate.

The same theory, according to most writers, can be applied to language acquisition.

Similarly, commas are used to separate an afterthought or a final phrase that contrasts with the main part of the sentence.

The war was vitally important for Europe, far more than it was for Britain.

To understand a particular culture we must look at the whole of society, not just its individual parts.

A single sentence can, of course, use commas in more than one way. In the following example, commas are used to separate an introductory phrase, punctuate a list and separate a final contrasting phrase.

To use the comma effectively, avoid overuse as this can make the sentence difficult to read and understand. Use the comma purposefully, as shown in the example above, and re-read a longer sentence to check the pauses are in the most helpful places.

Using commas to link simple sentences

A series of short, simple sentences can be jerky and tedious to read.

The University is large. It is close to the town centre. There are special rooms available. Advance reservation is necessary.

A way of improving the flow of the writing is to link sentences with a comma

together with a linking word (a co-ordinating conjunction) such as and, but,

so, or, nor or yet.

The University is large, and it is close to the town centre. There are special rooms available, but advance reservation is necessary.

Warning!

A comma cannot be used on its own to join two sentences. A comma only indicates a pause in a sentence; it can not join sentences without the addition of a co-ordinating conjunction. For example, these two sentences, whilst grammatically correct, would read better if joined.

The people followed their own creed. They were willing to die for it.

However, they can not be joined by using a comma on its own, as the comma shows only a pause, not a link.

X The people followed their own creed, they were willing to die for it. X

A comma together with a co-ordinating conjunction joins the sentences correctly.

The people followed their own creed, and they were willing to die for it.

Sentences can sometimes be joined effectively using a semi-colon (;). The companion leaflet, Using the Semi-colon and Colon provides a guide to its use.

Summary

If in doubt about your use of commas, read each sentence aloud, pausing briefly at each comma. If the sentence flows badly and seems jerky, you probably have too many commas. If you are breathless by the time you have reached the end of the sentence, you might need to insert some commas at appropriate points as shown in this guide. It may even be necessary to divide a very long sentence into two or more separate sentences.

Using paragraphs

Study guide

For a printer-friendly PDF version of this guide, click here

This guide explains how to make effective use of paragraphs in your writing. The function and features of a paragraph are explained, together with guidelines for using paragraphs to create a clear and coherent written structure.

Other useful guides: Using the comma, Sentence structure.

What is a paragraph?

Writing of any length requires subdivision into a number of points or stages, and these stages are expressed in a paragraph. Paragraphs, whether denoted by a new line and an indentation or a line break, provide a structure for your writing. The end of a paragraph represents a significant pause in the flow of the writing. This pause is a signpost to the reader, indicating that the writing is about to move on to a different stage. Each paragraph should deal with one idea or aspect of an idea, and it should be clear to the reader what this main idea is.