Cohesion is the explicit use of linguistic devices to signal the relationships between items within a text. Halliday and Hasan (1976) identify five types of cohesive device :
- Reference : John walked in. He looked around for a moment... where he refers to John.
- Ellipsis : John walked in and sat down. In this case, the subject of the second verb (again John) is retrievable from the context and therefore omitted.
- Substitution : I don't like cheese, but my husband does. Here does substitutes for likes cheese.
- Lexical cohesion : I spent so much money at the sales. I bought loads of things. The words spent, money, sales,and bought all belong to a common lexical field.
- Conjunction : Although it was raining, we decided to go for a walk. Here although signals the relationship between the propositions in the two clauses.
Cohesive devices like this help the listener/reader interpret the logical development of the discourse. However, a text may be coherent - ie capable of logical interpretation- without containing any such explicit linguistic connections. Widdowson (1978) gave the example
A : The phone's ringing!
B : I'm in the bath!
There are no cohesive ties linking these two utterances, but the second can easily be interpreted, through our knowledge of the world, as meaning I can't go and answer it because... The exchange is therefore coherent without needing to be cohesive.
Halliday, M.A.K and Hasan, R. 1976, Cohesion in English, Longman
Widdowson, H. 1978, Teaching Language as Communication, OUP