When you register a company as per the law of the land and start the business you call it startup when you have already registered a company to start business every aspect of starting a company is done.
In recent times is where the word startup was glorified and led to glamour of starting a company as startup. It doesn’t mean business was never started in earlier years yes they used to start business and call it have started business or started company.
Recently is where glorification took place of startups, lets understand when a startup becomes a company technically speaking it becomes a company when the startup is registered as per law of the land.
Whereas today a startup loses the tag of startup and becomes a company after having survived 3 years or the 1000-day rule or if its raises continue a series of funds and becomes poster boy of investors it loses its tag as startup superficially.
In olden days company would become a company only if it grew and survived on its own as those days venture capital funding was not there, so the companies which were started in 1980’s era used to become companies after a certain period of time when people would talk about the company.
In today it’s fashionable to say I have founded a startup or I am CEO of a startup or I work in a startup and it’s going to be big.