How do sentence-final particles add meaning in Sinitic languages?

In Sinitic languages, sentence-final particles are used to convey a variety of meanings that define the nature of the entire sentence or its predicate. These particles function to indicate specific communicative intents, such as a question, a command, surprise, or the emergence of a new situation.1

For example, in Modern Standard Chinese, the particle le is frequently used at the end of a sentence to signal a "new situation." This can indicate that an event has begun or that a state of affairs has changed, such as in xiayu le ("now it is raining") or bu lai le ("now there is no longer any chance that he will be coming"). While these particles are essential for adding grammatical and pragmatic nuance, it is noted that grammatical elements of equal or closely related values across different Sinitic languages are often not related in their sounds.21