to make a definite choice or come to a firm conclusion in a situation where more than one option or possibility is open

He decided on the blue shirt

to make a judgment

She decided in favour of the defendant

(often + to/that) to make a choice or come to a conclusion about (something)

I decided to go by bus

They decided that they couldn't afford a holiday

to influence (somebody) to make a choice or resolution

In the end, her screaming decided me and I left the room

to settle the outcome of (something)

Her goal decided the match