Coherence and cohesion

Coherence refers to how easy it is to understand the writing. If a paragraph is coherent, each sentence flows smoothly into the next without obvious shifts or jumps. A coherent paragraph also highlights the ties between old and new information to make the structure of ideas or arguments clear to the reader. Along with the smooth flow of sentences, a paragraph's coherence may also be related to its length. If you have written a very long paragraph, one that fills a double-spaced typed page, for example, you should check it carefully to see if it contains more than one controlling idea. If it does, you should start a new paragraph where the original paragraph wanders from its controlling idea.

Cohesion or flow means that all sentences are grammatically and lexically well connected. You can use different connectors in a paragraph, for example, classifiers, such words as idea, problem, issue, factor, solution, referents this, that, these, those, such, he, transition words and phrases signaling time-order, cause-effect, listing, or comparison/contrast. To connect ideas, you can also repeat the same word, if necessary, or use its word forms, e.g. reduce – reduction.

Cohesion with NO Coherence

"My favourite colour is blue.  Blue sports cars go very fast.  Driving in this way is dangerous and can cause many car crashes.  I had a car accident once and broke my leg.  I was very sad because I had to miss a holiday in Europe because of the injury."

As you can see, there is plenty of cohesion here.  The sentences connect clearly together but if you read the paragraph, it really makes no sense - I start talking about blue and I finish talking about a holiday in Europe.  There is no coherence in this sentence.

Coherence with NO Cohesion

"My favourite colour is blue.  I'm calm and relaxed.  In the summer I lie on the grass and look up."

This is more difficult to understand but, basically, this lack of cohesion means a lack of sufficient connectors to join the ideas together.  If I try hard, I can understand what the person is saying: a short answer, an explanation, an example; however, the sentences don't fit together.

Theme and rheme

Flow of information in paragraphs

In order for a paragraph to be easy to read, the information in it must flow easily from one sentence to the next. To do this it is important to structure your information clearly and signal exactly what you want to say by the use of signalling words.

Information structure

Most sentences in English have two parts a theme (or topic) and a rheme (or comment). The theme is what you are writing about - it is shared information and it has been introduced to your reader. The rheme is what you are saying about the theme - it is new information, what you want to tell your reader.

1. The M1 goes from London to Leeds.

2. The motorway from London to Leeds is called the M1.

The theme in sentence 1 is "the M1". The reader has been introduced to the M1 but does not know where it goes and therefore needs to be told. In sentence 2, the theme is "the motorway from London to Leeds". The reader knows there is a motorway from London to Leeds but does not know what it is called.

In English the theme usually comes at the beginning of the sentence and the rheme at the end. The decision about which part of the sentence to make the theme and which part to make the rheme depends on the information that needs to be communicated. This depends on the sentences that come before.

3. I was born in Glasgow. Glasgow is the largest city in Scotland.

4. I was born in Glasgow. The largest city in Scotland is Glasgow.

All the sentences are grammatically correct but in example 4, the information to be communicated, the rheme - the largest city in Scotland, is at the beginning of the sentence. Example 3 is preferred in English.

There are two basic choices in organising information texts:

1. The rheme of one sentence becomes the theme of the next sentence.

The complete electrical behaviour of any valve or transistor can be described by stating the interrelation of the currents and the voltages between all the electrodes. These relationships can conveniently be displayed graphically, and the various curves are known as the 'characteristics' of the device. In principle, all the characteristics should be available to the designer proposing to use the device in a circuit. (W. P. Jolly, (1972). Electronics, p. 61)

2. The theme of one sentence is the same as the theme of the next sentence.

Anthropology is the study of humankind, especially of Homo sapiens, the biological species to which we human beings belong. It is the study of how our species evolved from more primitive organisms; it is also the study of how our species developed a mode of communication known as language and a mode of social life known as culture. It is the study of how culture evolved and diversified. And finally, it is the study of how culture, people, and nature interact wherever human beings are found. (Marvin Harris, (1975), Culture, people nature, p. 1)

What happens when you begin a sentence with new information?

Your reader gets a new idea without any context. He or she may try (incorrectly) to link this information to the previous sentence. After reading the rest of the sentence, the reader may have to revise his or her understanding. If you do this too much, it makes your writing confusing because it lacks cohesion. Going backwards like this slows the reader down and takes energy. Beginning sentences with old information makes writing cohesive. It also allows you to put new, important information in the position of emphasis at the end of the sentence.