purpose
The German word 'Zweck' translates to 'purpose' in English. It is used to describe the reason or intention behind an action or thing. For example, one might say 'Der Zweck dieser Maschine ist es, Brot zu backen,' meaning 'The purpose of this machine is to bake bread.'
The end justifies the means.
This is a proverb where 'Zweck' is used to mean 'end' or 'objective'.
What purpose do you use the device for?
In this sentence, 'Zweck' is used to refer to the specific goal or reason for using the device.
There's no point in complaining.
In this context, 'Zweck' means 'point' or 'use' considering the futility of complaining.