shut down
With or without an object
Stop operating (a business or computer)
The system shut down without warning.
With or without an object
It can be used with no object, and it can also take one. With an object it is usually separable: turn the volume up, turn it up.
The particle: down
This verb belongs to the group ‘breaking and closing’.
Others in the group: break down, close down.
Practise it
Add it to your daily practice or see every verb with down.
Further reading: shut down on Wiktionary (CC BY-SA).