'in v on somebody's mind'?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hi,

What is the difference between ‘in somebody’s mind’ and ‘on somebody’s mind’?

Thank you very much.

2

The version with “on” has a stronger and more specific sense that someone is preoccupied with or concerned about something, so they are thinking about it repeatedly over a period of time.