In the UK, a "sole trader" is a freelancer or entrepreneur who works for him- or herself. He or she has neither entered into partnership with others nor formed a limited company. I am a sole trader. I fill in one tax return for my all my income. It is a formal term used for accounting and tax purposes, but is widely known in the business world. An entrepreneur is a more general word for someone who tries to find and develop business. An entrepreneur could be a sole trader or could work within other legal structures. You don't need the word "private" with entrepreneur - it adds no meaning. Your usage of the word "leader" is not known as a synonym for either sole trader or entrepreneur. It may be a direct translation. A "seller" is a person who sells things. It is a very general word. It is not a synonym for the other words. If you also want to know terminology in use in the USA or other English-speaking countries, I recommend that you ask.