Interesting question I must say.
Purpose is the reason we were born,it's the reason we exist.
Everyone was born with a purpose, nobody is a mistake or an accident.
There is something God wants done that's why he gave birth to us..
We don't get to choose our purpose,we have been predestined by God for it..
God speaking to Jeremiah,he said, before I formed you in your mother's womb I already know you and have ordained you to become a prophet. Inother words we are born to fulfill God's plan and purposes.
We can't have more than one purpose in life,it definitely has to be specific..
We may be involved in other vocations but we do have one definite purpose.