You use rely when you trust people or things to do something. It means you believe they will help or be right.
I rely on my friend for help.
We rely on the bus to go home.
Rely can mean that you use a fact or a source to decide or do something. You trust the information to be true.
We rely on data to make choices.
She relies on facts for answers.
Here, rely means you believe something will happen or will be there when you need it. You trust it is sure.
You can rely on the sun to rise.
They rely on good weather for the trip.
Here, rely means you trust people will give you support or help, especially in hard times.
She relies on her family for comfort.
He relies on friends when sad.
