吗 and 吧 at the end of a question

Question

I heard that ba (吧) can be used at the end of a sentence just like ma (吗). Per my understanding, it's not interchangeable with ma (吗) but a more playful way of asking the same question. (Some girl said I should use 吧 when asking her if she wants to go to lunch, idk what that means.)

So, when do you use each of these words? What are the connotations of each?

Answer 1

Firstly, you are correct... both can be used at the end of a sentence, but they do not have the same meanings.

吗 ma = question particle

吧 ba = suggestive particle

Here's some examples:

你还好吗？(Nǐ hái hǎo ma) Are you okay? 

你还好吧。(Nǐ hái hǎo ba) Come on, you're okay, right? (suggesting that they're okay)

Or, In many cases 吧 is in response to 吗:

Person A: 好吗？Okay?
Person B: 好吧。 Fine...

That girl said you should use ba because she thought you should be more suggestive

我们一起吃饭吧！（Wǒmen yīqǐ chīfàn ba）sounds more assertive than 你想跟我一起吃饭吗？（Nǐ xiǎng gēn wǒ yīqǐ chīfàn ma?）