In business and finance, a share (also referred to as equity share) of stock means a share of ownership in a corporation (company). In the plural, stocks is often used as a synonym for shares especially in the United States, but it is less commonly used that way outside of North America. In the United Kingdom, South Africa, and Australia, stock can also refer to completely different financial instruments such as government bonds or, less commonly, to all kinds of marketable securities.

Stock typically takes the form of shares of either common stock or preferred stock. As a unit of ownership, common stock typically carries voting rights that can be exercised in corporate decisions. Preferred stock differs from common stock in that it typically does not carry voting rights but is legally entitled to receive a certain level of dividend payments before any dividends can be issued to other shareholders.

Convertible preferred stock is preferred stock that includes an option for the holder to convert the preferred shares into a fixed number of common shares, usually anytime after a predetermined date. Shares of such stock are called convertible preferred shares (or convertible preference shares in the UK).

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning the island of Great Britain, the northeast part of the island of Ireland, and many small islands.

Northern Ireland is the only part of the UK with a land border, sharing it with the Republic of Ireland. Apart from this land border, the UK is surrounded by the Atlantic Ocean, the North Sea, the English Channel and the Irish Sea. The largest island, Great Britain, is linked to France by the Channel Tunnel.

A stock derivative is any financial instrument which has a value that is dependent on the price of the underlying stock. Futures and options are the main types of derivatives on stocks. The underlying security may be a stock index or an individual firm s stock,single-stock futures.

Stock futures are contracts where the buyer is long, takes on the obligation to buy on the contract maturity date, and the seller is short, takes on the obligation to sell. Stock index futures are generally not delivered in the usual manner, but by cash settlement.

A stock option is a class of option. Specifically, a call option is the right (not obligation) to buy stock in the future at a fixed price and a put option is the right (not obligation) to sell stock in the future at a fixed price. Thus, the value of a stock option changes in reaction to the underlying stock of which it is a derivative. The most popular method of valuing stock options is the Black Schools model. Apart from call options granted to employees, most stock options are transferable.

First company to issue shares of stock after the Middle Ages was the Dutch East India Company in 1606. The innovation of joint ownership made a great deal of Europe's economic growth possible following the Middle Ages. The technique of pooling capital to finance the building of ships, for example, made the Netherlands a maritime superpower. Before adoption of the joint-stock corporation, an expensive venture such as the building of a merchant ship could be undertaken only by governments or by very wealthy individuals or families.

The price of a stock fluctuates fundamentally due to the theory of supply and demand. Like all commodities in the market, the price of a stock is directly proportional to the demand. However, there are many factors on the basis of which the demand for a particular stock may increase or decrease.

These factors are studied using methods of fundamental analysis and technical analysis to predict the changes in the stock price. A recent study shows that customer satisfaction, as measured by the American Customer Satisfaction Index (ACSI), is significantly correlated to the stock market value. Stock price is also changed based on the forecast for the company and whether their profits are expected to increase or decrease.