[susan53]

Any simple tool or instrument which isn't working properly or at all can be described as "broken". For example :

- Don't take any notice of that thermometer - it's broken.
- I didn't make a cake because my food mixer is broken.
- I'm sorry it's so hot in here. The fan is broken.

The more complex the system or machine, the more likely it is that "break down" will be used instead.

- I had to walk up eight flights of stairs because the lift had broken down.
- I'd offer you a lift, but my car has broken down