Last month we looked at how to organize a sentence. The fundamental idea was that the parts of the sentence should be clearly organized. Usually a sentence should start with the most important fact and the other details should follow logically from that. The same is true of a paragraph.

Just as it is a good idea to put just one fact in a sentence, we should have just one idea per paragraph. In fact, this is the whole point of a paragraph. It is putting a group of sentences together to make one idea.

This is why there is no such thing as the 'proper length' for a paragraph. In fact, if you look at some newspaper articles, you will see that a paragraph is sometimes a single, short sentence. For example, in the following extract we can see a very short paragraph indeed:

'Do we have to accept that a growing population will constantly consume more resources? Is it inevitable that our environment will become more degraded and that shortages will become a way of life? Are we, in short, set on an inevitable downward path?
    No.
When we look at the history of the human race … .'

Here we see a paragraph of just two letters ('No'). However, this little paragraph has a different purpose the the paragraphs that come before and after. The first paragraph presents a list of questions. Then in the next paragraph the author tells us that he thinks that the answer to all these questions is 'no'. In the paragraph after that, the author goes on to explain his reasons. Each paragraph has a separate purpose and central idea. We cannot combine the paragraphs without losing the clarity and force of the original text.

Therefore when writing, or editing our writing, the two questions to ask of a paragraph are; 'what is the central idea in this paragraph?', and 'are all the sentences in this paragraph related to this idea?'

Often the central idea is put in a single sentence, often at the start or the end of the paragraph. This is sometimes called the 'topic sentence'. It is a good idea, especially with discursive writing, to include a topic sentence so that the reader clearly understands what the writer intends to say in a particular paragraph. However, topic sentences also work with other types of writing.

Here for example, in a descriptive paragraph, we see the topic sentence used twice for emphasis:

'John was fat. Sometimes a fat person might be called 'chubby' or 'a bit overweight', or even 'sturdy' and 'robust'. However, such gentler adjectives fled the mind after even a brief look at John's rolling chins, sagging chest and the enormous belly that strained against his over-sized shirt and trousers. There was simply no getting away from it. John was fat.'

This paragraph has a single idea. This is stated in the topic sentence and developed in the rest of the paragraph. You will notice that the paragraph also has direction – the description starts at John's chin and moves downwards. Usually the 'direction' of a paragraph is less literal than this, but a well-organized paragraph unfolds in a logical manner.

To help the reader to follow the flow of ideas, it is important for a writer to use link words and sentences. These explain how the idea of the paragraph is linked to the ideas that come before and afterwards, and also clarify the development of the idea within the paragraph.

So far, we have considered the dandelion as a weed. But what if we consider it as a flowering plant in its own right? After all, it has a cheerful, bright yellow flower and unique and attractively-shaped leaves. Furthermore, it is hardy - indeed as many gardeners well know, almost indestructible – and requires minimum effort to grow and maintain. So why should a flower bed of dandelions not be as visually appealing as a bed of marigolds or daisies?

Here, the paragraph is linked to the preceding paragraph by the first sentence. Then comes the topic sentence in the form of a question. The argument is developed with the link words 'After all' and 'Furthermore' before reaching a conclusion introduced with the words 'So why'. This creates a logical chain which is easy for the reader to follow.

• A paragraph should have a single idea
• This idea can be stated in a 'topic sentence'
• Other sentences in the paragraph should explain or develop this idea
• All sentences should have a logical sequence
• This sequence should be made clear by link words
• The paragraph should be linked to the ideas of the surrounding paragraphs in a logical manner.