吧 is a commonly used particle that will soften the tone of a command, suggestion, supposition, or statement. It can also indicate reluctant agreement.
Let's look at some examples of how we can make commands sound a bit more polite:
command + 吧
The English sentences still sound a bit harsh, sure, but if you wanted to sound more polite, you’d have to reword your commands entirely! However, the simple addition of 吧 to the Chinese sentences makes them sound much more polite without having to reword them.
suggestion + 吧
When we want to express uncertainty in our supposition and look for confirmation, we could add 吧 with a question mark at the end of it.
supposition + 吧 + ?
This may seem similar to 嗎, but, where 嗎 is a direct yes-no question,吧 is a request for verification of something you think you’re probably right about.
There are time we don't want to be too accusatory or harsh when making a statement, especially when it’s something unpleasant to hear. Adding a 吧 at the end of our statement will help make it gentler.
statement + 吧
Sometimes even if we agree to something, we might not be completely happy about it, or we have some hesitation about it. In this case, we will add 吧 after our agreement.
agreement + 吧
In the last dialogue, we can see two different uses of 吧. The one who wants to break up adds 吧 at the end of his statement to soften his tone (he may want to break up, but he at least wants to be gentle about it), and his partner accepts it even though she doesn't want to.