What term refers to a piece of ownership in a company or investment vehicle?

The term that refers to a piece of ownership in a company or investment vehicle is "stock." When an individual purchases stock, they are essentially buying a share of the ownership of that company. This ownership can provide rights, such as voting on company matters or receiving dividends, which are a portion of the company’s profits paid out to shareholders. Stocks represent a claim on part of the company's assets and earnings, making them a fundamental component of investing in the stock market.

The other terms provided in the options refer to different concepts. A bond represents a loan made by an investor to a borrower, typically a corporation or government. A dividend is a distribution of a portion of a company's earnings to its shareholders and is usually paid in cash or additional shares. Equity is a broader term that refers to ownership in a general sense, which can include stocks, but is not as specific as saying "stock" directly.