What term describes a part ownership of a business, such as holding shares?

The term that describes a part ownership of a business is equity. Equity refers to the ownership that shareholders have in a company, represented through shares. When individuals own shares, they essentially own a part of the company, entitling them to a proportionate share of the company’s profits and assets. Equity also reflects the value of shares in the company's total capital.

While shares are the actual units of ownership that can be bought and sold, the broader concept of equity encompasses the total ownership interest in the company, which includes all shares held collectively. Therefore, the most complete answer aligning with the concept of part ownership within a business is equity.