A down tick occurs when a stock trades at a price lower than the current bid or offer. A zero-plus tick happens when a stock up ticks on a trade and the following trade is executed at the same price level. On Nasdaq stocks you may short a stock only on an up tick or a zero-plus tick. Also referred to as the print. To ignore a customer's order that is priced better than the inside quote and to continue to trade at the inferior quote.
Time constraints vary for each type of order.
Restraints initiated by the New York Stock Exchange to prevent program trading if the Dow moves 2 percent in either direction from the previous trading day's closing price. Stops that are moved in the direction of the trend to protect profits. The expiration of stock options, index options, and futures on the same day, an event that happens once each quarter. A market in which the firm making the market in a security is both buyer and seller and must maintain firm bids and firm asks. Nasdaq market makers and NYSE specialists both make a two-sided market in the stocks they handle.