In talk-in-interaction, discourse units play a particular role. A discourse unit is a turn-constructional unit (see units in our method that is longer than a phrase. This part of the grammar describes the types of discourse units that we know of so far.
The person, who has the turn in a conversation, normally has the right to utter only one sentence before others can begin to speak. But a speaker can also obtain the right to speak for a longer time, and one way of doing this is by introducing a discourse unit.
Discourse units are storytellings, accounts and listings. There are basically two types: (1) “closed discourse units” where it is clear from the beginning that it is a discourse unit, and the speaker and the recipient “agrees” that the speaker has the right to utter a discourse unit; and (2) “open discourse units”, where it becomes clear step by step that it is a longer unit.
The difference between a closed and an open unit is not always obvious (neither for the person analysing the conversation nor for the participants in the conversation). But typically, a closed discourse unit is a storytelling where the participants have established that now a story is going to be told, and they have distributed the roles of story-teller and story-recipient between them. Open discourse units can be so-called “three-part lists”, where one does not realize that something is a listing until hearing the second part, and thereby one knows that it is a longer project (or a discourse unit).