A stock symbol, or ticker symbol, is a sequence of characters assigned to a particular company's stock by a stock exchange. The NASDAQ, AMEX and New York Stock Exchange are the primary exchanges in the United States that identify individual stocks with character-based symbols, according to Investopedia.
The AMEX and NYSE exchanges use three-letter symbols to identify particular stocks, while the NASDAQ uses four- or five-character symbols, according to Investopedia. The optional fifth character in a NASDAQ stock symbol provides insight into the stock's history. For example, a Q indicates bankruptcy while F indicates foreign issues with the stock.
Online search tools, such as the NASDAQ Symbol Lookup, allow users to find company stock symbols by searching for a full or partial character string.