One of the key frameworks I use as a business coach analyses the Stages of a business' development. Startup is the first stage in that lifecycle.<p>It <i>is</i> possible to "have been around for five years, generate millions in revenue, and have fifty employees" and still be in the startup stage, especially if your vision is to generate billions and have thousands of employees; conversely, some businesses in an Advanced Growth stage would not have those numbers (except, probably, the time in business).<p>To take those differences into account, our Stages framework relies on the changing <i>feelings</i> that occur within an organisation, rather than things like turnover and profit (which are easily compared, but not necessarily comparable). Loosely, I define a business as moving out of Startup when it begins to 'invest with confidence' rather than 'investing with hope'.<p>That business you have in the garage making no money? You're probably investing your time and some cash with the hope it will succeed. Google? They're investing with confidence, because they've demonstrated their business model. Twitter? Is a good question - are they feeling hopeful and frantic, or confident?