A sole-proprietorship is a business owned by one person or one company. There are no partners. The sole-proprietor has absolute say in the running of the business.
Under the Business Registration Act, Cap. 32, "business" includes every form of trade, commerce, craftsmanship, calling, profession and any activity carried on for the purposes of gain but does not include any office, employment or occupation, or any of the businesses specified in the First Schedule (List of exempted entities / individuals).