Nearly everyone uses discourse markers in speech and in writing, and they can be found in all languages. Discourse markers (DMs) are words that have no effect on the coherence or grammar of a sentence, such as the words "well" or "so" and the phrase "you know" in English. Instead, discourse markers help make discourse structuring more coherent and flow better. At one time, discourse markers were thought of as mere speech fillers, but discourse analyzers now realize that although these markers have no actual purpose within the discourse, they perform their own functions in speech. They are mostly used as transitions in subject or thought, methods of stressing thoughts and response signalers to previous utterances by another speaker.
Discourse markers make a conversation livelier, personal and involved. Without them, conversation can be stagnant and awkward. People tend to take pauses during dialogue, typically after a refusal, compliment or request. If this naturally occurring delay in speech is met with complete silence, the conversation becomes socially awkward. The addition of DMs keep the conversation flowing.
Other times when DMs usually happen are when showing surprise, for clarification, when shifting topic and when resuming previous topics. What makes a discourse marker useful is that in just a word or short phrase, it removes the guesswork from the previous dialogue and from the current and upcoming discourse. It also can signal to the listener or reader what to expect.
When placed at the start of a thought, a discourse marker is usually a reaction toward the other speaker. For instance, "well" can mark a response to the statement made by the other speaker. When placed at the beginning of a thought, it might also signal the end of mystery or anticipation. Another example of this would be the use of "so" during an introduction such as, "So, it is my pleasure to introduce ... ."
Some words and phrases are used as both purposeful parts of a sentence and as discourse markers. An example of this is the discourse marker "you know." In the sentence, "You know, I don’t like cheese," the phrase "you know" is a discourse marker. In the sentence, "Do you know where the book is?" the phrase is no longer a DM. This interchangeability can make it difficult to distinguish some DMs from the actual conversation.
To determine whether a phrase or word is a discourse marker, one must consider the context of the dialogue. Taking the word or phrase from the sentence may also help. The sentence should be able to stand on its own without the discourse marker.