"Stock" is an instrument that represents an ownership position in a corporation. The percentage ownership in the company is determined by the number of shares of stock held divided by the total number of shares outstanding. For example, if a stockholder has 100,000 shares and the company has a total of 1,000,000 shares outstanding, the stockholder owns 10% of the company. Stock is typically either common stock or preferred stock (preferred stock has a priority over common stock in the liquidation or sale of the company).