1. COHERENCE

2. If a text is coherent, it makes sense.
The following text lacks coherence.
If there is a fault with the toilet please call ext Place in water halfway up basin. That’s where all the salty water comes from.
It lacks coherence because;
It is difficult to see how the sentences relate, even though they have some shared elements (toilet, water, basin).
They do not relate to each other, nor does the whole text relate to anything in our background knowledge of the world.
Furthermore, the text doesn’t resemble any kind of text we are familiar with.
The next text is more coherent.

3. We want you to be delighted with this facility
We want you to be delighted with this facility. If there is a fault with the toilet please call ext on the nearest white courtesy phone.
We now recognize the test as belonging to the type public notices. The language and organization are appropriate, especially when we know it was written to be read in an airport restroom.
Moreover, the two sentences have a logical relation. You could put a linking word, such as so between them.
Likewise, the following sentence makes sense:
That’s where all the salty water comes from.
When we discover it is the (humourous) answer to this question in a newspaper.
Question: Do fish sweat?

4. So, coherence is achieved when (among other things) a text follows certain rules.
There is a consistent topic.
The sentences have a logical relation to each other.
It is relevant to it’s context.
It can also help if there are clear links between the different part of the text, this is called cohesion – but this is not the same as coherent. It is possible for a text to be coherent without being cohesive. For example:
Remove lid. Add water to the fill mark. Stir well. Leave for two minutes. Stir again.

5. COHESION

6. If a text is cohesive, its elements are connected.
Cohesion is the use of grammar and lexis to achieve connected text, either spoken or written.

7. ACHIEVING
COHESION

8. The main cohesive devices in English are these.
Lexical:
Repetition of words, or words from the same word family (e.g. coherent, cohesive, cohesion) or the use of synonyms.
Use of general words like (the place, the girl, the facility) to refer to something more specific that is mentioned elsewhere in the text.
Using words from the same theme (texts, readers, written)
Substitution – replacing previously mentioned words with one / ones.
Ellipsis – leaving out a word because it is already know.

9. Grammatical:
Reference words – especially pronouns (it may help)
Determiners (e.g. this, that)
Substitution – replacing previously clauses with do/does or so/not
Ellipsis – leaving out previously mentioned words
Linkers – using linking words such as therefore, what’s more, then
Parallelism – sentences that “copy” the structures of previous sentences.

10. The Observer Sports Monthly, January 2011. Back Cover
Can you imagine being a 222-car family? Sounds crazy. But in Singapore it happens. There they have a big pool of cars. Honda cars. And everyone shares them. You use one when you need it. Drop it off when you don’t. We call it the Intelligent Community Vehicle System. It’s like one big happy car sharing family. Perhaps one day we’ll make it happen here. Do you believe in the power of dreams?
The Observer Sports Monthly, January Back Cover

11. The Observer Sports Monthly, January 2011. Back Cover
Can you imagine being a 222-car family? Sounds crazy. But1 in Singapore it2 happens. There3 they have a big pool of cars4. Honda cars5. And6 everyone shares them7. You use one8 when you need it9. 10Drop it11 off when you don’t We call it14 the Intelligent Community Vehicle15 System. It’s16 like one big happy car17 sharing family19. Perhaps one day we’ll make it20 happen here. Do you believe in the power of dreams21?
The Observer Sports Monthly, January Back Cover