I don't agree. Startup has a fairly specific task or operating style that is irrelevant to its size and age and number of employees. A startup is a company that is experimenting with ideas and its main goal is to validate a business model. If those business models can't be validated in a certain amount of time, the company should shut down. If a business model is validated it needs to be implemented and the company is no longer a startup.

You can be a 0-day 1-person company but if you have a business model and an operating structure, you're not a startup. Most companies are started on a specific business idea and planned to run for long term on that idea. Those are not startups.

Where do you draw the line for "validating a business model"?

Uber was founded 11 years ago. How long do you need to validate the business model of a taxi app?

AirBNB was founded nearly 12 years ago. How long until they're done validating the business model of letting people rent apartments over a website?

I feel like a business model is validated when it becomes profitable, which it's why many of us don't validate the Uber/Lyft business model yet.

Okay, so it's partially computable. But non-viability can never be proven?