Coherence is sometimes called cohesion, even though some would claim that the two terms denote phenomena that are obviously related, but clearly different. We use coherence to cover both the extent to which a text hangs together, as it were, and the various linguistic and structural means of achieving this coherence.
In a coherent text, there are logical links between the words, sentences, and paragraphs of the text. The term comes from the Latin verb co-haerere, which means 'to stick together' (OED). Another way to describe coherence is to say that it has to do with good and smooth text flow. A writer must maximise understanding of a text by making it as clear and logical as possible.
Coherence can be achieved in a number of ways. Oshima & Hogue (2006) suggest the following four:
- Repeating key nouns
- Using consistent pronouns
- Using transition signals to link ideas
- Arranging your ideas in logical order
Starting with the last point, for the reason that it is a paramount aspect, any academic text will be incomprehensible unless the ideas expressed in it are arranged in some sort of logical fashion.
There are several different kinds of logical order, but some of the more frequently used are chronology, importance, and contrast. Chronology, firstly, has to do with time, and in terms of logic, events are ordered in a sequence. Secondly, importance means that ideas are discussed in a sequence which implies either a increasing or decreasing order of importance. Thirdly, contrast has to do with ordering ideas by contrasting or comparing them.
The last but one point - transition signals (sometimes called linking words or linking adverbials) - has to do with the use of specific words and phrases that evoke links and transition between ideas.
As was emphasised above, there is no substitute for ordering the various ideas and parts of a text in a logical way. However, even when this is done in a satisfactory manner, there is often a need to strengthen the organisational pattern of a text passage by inserting logical markers.
There is a multitude of words and phrases like these, and they can be grouped in different classes based on the function they serve. The link below will take you to a list of different transitional and linking words.
The point called using consistent pronouns has to do with substituting nouns with pronouns in an effective way. A text that does not use pronouns to some extent will come across as overly repetitive. The important part when using pronouns is to be consistent by using the same person and number throughout the paragraph or text. Click on the link below to see a comparison between a text with and without pronouns.
The fourth way to achieve coherence in a text passage is to repeat key nouns. However, even if nouns typically are the words that should be repeated, also words from other word classes can be repeated if they are central to the topic of the text. There is no set rule as to how often a key noun can be repeated - the guiding principle must be clarity and an avoidance of making the reader feel that there is too much repetition.
An alternative to repeating a key noun over and over is to use another noun that has the same, or at least very similar, meaning: a synonym.
Click on the link below to see an example of effective repetition of key nouns.