Stock splits simultaneously increase the number of shares available for purchase and decrease the price. The total market value of the trading shares remains the same.
A company might decide to increase its stock's price through a reverse split. In a two-for-one reverse split, the number of shares is cut in half while the price increases proportionately.
Just as it can issue additional shares, a company can repurchase, or buy back, shares of its stock. When a company repurchases shares, it takes them out of the secondary market and increases each shareholder's relative stake in the company.
If a corporation issues new shares, it must give existing shareholders the first opportunity to purchase new shares. This is called a Rights Offering.
A warrant gives the stockholder the right to purchase stock from the issuer at a specific price within a certain time frame. Warrants are similar to rights, but typically have a longer time horizon, usually measured in years.
Common reorganizations include mergers & acquisitions and bankruptcy.