I'm going to say a startup is something that can satisfy some formula that takes into account a set of attributes like, size of the company in terms of employee

I'm going to say a startup is something that can satisfy some formula that takes into account a set of attributes like, size of the company in terms of employees, revenue, age, users, etc... If the result is below some threshold then we call it a 'startup' else maybe it's a corporation.. Now I have no idea what that formula is, but I'm guessing its some calculation that we all do in our head based on our own ideas and in the end we say 'yup.. it's a startup..' or not. At some point Google, Facebook, LinkedIn, Groupon etc.. all surpassed that level of 'Startup' and moved into the 'Big Company' field. Can any math geeks out there put together something that reflects that ?