Suppose I'm to live in France, working there. How big a vocabulary shall I have, or, how many words shall I know, in order to be able to survive there? I know this question is a bit vague, but please just try give some ball-park number? 2000? 5000? 10000?
What I meant with "survive":
When I first went abroad from China, my English was barely enough to "survive". For example, I sometimes forgot to use "stamp", instead I will ask post office officers "How can I buy some post ticket?"
So this survive, is just to live for basic needs, buying apparels, going to a restaurant, rent a flat, take transportations, and of course, work.
As I was just a VB programmer, working is also manageable with a limited vocabulary — I'm not a salesman or product owner that need talk to customers everyday.
Hope this explains my "concept" of "survive"…