Sometimes the words we say can sound harsh or demanding, even when that is not our intention. Mandarin has a way of softening requests or suggestions by adding the final particle ba 吧.
Using the final particle ba is equivalent to using a question tag (aren't you?) or making a suggestion in the form of "let's (do something)" - "let's go to the movies."
The final particle ba is always used at the end of a sentence.
Probability
When the speaker believes the listener will agree, the final particle ba is used to indicate probability. In this situation, dà gài 大概 can be used in the sentence.
Examples of the Final Particle Ba
Wǒmen zǒu ba.
Let's go, OK?
(trad) 我們走吧。
(simp) 我们走吧。
Nǐ gàosu tā ba.
You tell him, OK?
(trad) 你告訴他吧。
(simp) 你告诉他吧。
Nǐ (dàgài) hěn máng ba?
You are (probably) very busy, aren't you?
你(大概)很忙吧?