Economic theory of entrepeneurship
Cantillion: An entrepreneur is a risk-taker. Instead of workers taking the risk of not getting their goods sold the entrepreneur takes this risk and guarantees the workers their income.
Knight: An entrepreneur is a bearer of uncertainty. Uncertainty is not the same thing as risk. Risk comes from recurrent events, which gives knowledge of possible loss. Uncertainty, on the other hand, comes from unique events where prior knowledge is lacking. Possible loss can only be estimated. Risk is ensurable while uncertainty is not. Profit is a reward from bearing uninsurable risk.
Schumpeter: The entrepreneur is a hero that utilizes other's inventions and finances to pursuade a dream.
Marshall: There are many entrepreneurs in society that are not heroes but nevertheless great contributors to economic growth. These small campanies are called "low-level" entrepreneurs.
Austrian school: An entrepreneur is a market middleman that takes initiatives to trade by exploiting price differences on the market. The entrepreneur is a dealer rather than a company leader.