Guide:Discourse Particles
Discourse particles are used very little in conlangs and are not extremely well understood, yet we humans use them perfectly without issue in our native tongues, but at the same time it is one method we use easily to identify foreign speakers.
What are discourse particles? Discourse particles are small words or phrases that add no information to the sentence itself; the truth value of the statement remains intact. For example, the two sentences "He was at the shop" and "Well, he was at the shop" contains the same amount of information, but the "well" differentiates them. "Well" does not add any content information, he was still at the shop, whoever "he" is. So what is the real difference? The difference is that "well" here conveys discourse information. In English it typically attempts to convey information that listener might not like about the information being presented and prepares them for this.
Discourse particles do not need to be even "words" per say, there are plenty of them that are not considered words and just "noises" we make. "Um" is a classic example; it means something along the lines of "the speaker is trying to think of something and does not want their turn of speaking being interrupted". So, in essence "um" is saying "I'm still talking, give me a moment to think about what I am trying to say and don't take my turn away from me".
"Uh-huh" or "mhmm" can be seen as saying "I hear what you're saying and might agree, please continue as I have been listening so far".
Discourse particles commonly convey the speaker's attitude, their expectations of how the listener will react or feel about information.