The modal particle 吧
A modal particle (语气词) is a function word that adds additional semantic meanings to the sentence or emotionally colors it. It is usually placed at the end of a sentence.
The 吧 
particle has several functions. It can express:
1) suggestion and command.
It can be translated as “let’s”, “let”.
particle has several functions. It can express:
1) suggestion and command.
It can be translated as “let’s”, “let”.Examples
我介绍我的丈夫吧
Let me introduce you to my husband
wǒ jièshào wǒ de zhàngfu ba
快出门吧！
Exit a little faster!
kuài chūmén ba
Pay attention
The particle 吧 softens the tone of the statement by removing the commanding tone of the imperative sentence.
2) agreement.
It is not usually translated in any way.
Examples
好，我问她一下吧！
Okay, I'll ask her!
hǎo wǒ wèn tā yíxià ba
好吧
Okay
hǎo ba
3) guessing and assuming in a question sentence.
It can be translated as “must be”, “most likely” or not translated at all.
Examples
你新生吧？
Are you a new student? (I think you're a new student, aren't you?)
nǐ shì xīnshēng ba
你要买水果吧？
Do you want to buy fruits? (You must want to buy fruits?)
nǐ yào mǎi shuǐguǒ ba