NASDAQ, as defined by the Encyclopedia Britannica, is "an American stock market that handles electronic securities trading around the world." According to NASDAQ itself, the acronym is short for National Association of Securities Dealers Automated Quotations.

History

According to Britannica, NASDAQ was started in 1971 by the National Association of Securities Dealers, was merged with the American Stock Exchange in 1998, and is now "the largest electronic stock market (in terms of both dollar value and share volume) in the United States."

Stock Averages (or Indices)

NASDAQ, like other stock exchanges, compiles averages (also called indices) of stock prices throughout the trading day. As Matt Krantz of USA Today explained in a 2005 column, "each of these popular measures is an index, which is a basket of stocks selected for a specific reason to represent a larger group."

NASDAQ Average

The most often quoted number in news reports concerning the NASDAQ is the average representing all of the securities traded on the exchange.

NASDAQ 100

According to NASDAQ, the NASDAQ 100 Index "includes 100 of the largest domestic and international non-financial securities" listed on the exchange.

PMI and AHI

NASDAQ-100 also lists a Pre-Market Indicator (PMI) regarding trades before the official trading day (those that happen from 8 a.m. to 9:30 a.m. Eastern), and an After Hours Indicator (AHI) for trading after hours (4 p.m. to 6:30 p.m. Eastern).

Source:

Britannica.com: Definition of NASDAQ

USAToday.com: Matt Krantz, market numbers

NASDAQ.com: 100 Index

More Information:

NASDAQ.com

NASDAQ.com: PMI and AHI Definitions