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]
(..) ARIADNE: Like a coin? ARTHUR: No. It needs to be more unique than that. Like, this is a loaded die. No, I can't let you touch it. That would defeat the purpose. See, only I know the balance and the weight of this particular loaded die. That way, when you look at your totem... (..)2010 Inception