She knew from a young age that her sole 'purpose' (in life) was to be a writer. [=she knew that all she wanted (in life) was to be a writer]
We were happy to know that the money was being used 'for a good purpose'. [=for something useful, important, etc.]
There's little/no 'purpose' in restarting the process. [=there is little/no reason to start the process again]
(..) I'm on it. - How long do you think it'll take you? One hour. - Outstanding. Installing your system in the Hubble is the purpose of this mission and so we appreciate your patience, Doctor. Kowalski, we... we know you don't care about things like this, but, uh, for your information, this (..)2013 Gravity