Bust or burst?

For things that come apart with sudden violence you say ‘burst’.

The water balloon has burst.

In everyday speech, you can also say ‘bust’, but it’s considered slang.

Don’t bust the balloon.

‘Bust’ means to break and again is used informally.

I busted my arm playing football.

Usually you would say ‘I broke my arm playing football’.

To ‘go bust’ is to go bankrupt or lose all your money.

To ‘be busted’ is to be caught doing something illegal.

And if you say you are ‘busting’, you mean that you urgently need to go to the toilet.

You say ‘burst’ and not ‘bust’ in the expressions ‘burst into tears’ and ‘burst out laughing’.