Odd lot - A trading order for less than 100 shares of stock. Compare round lot.

Offer - Indicates a willingness to sell at a given price. Related: Bid

Offset - Elimination of a current long or short position by making an opposite transaction. Related: Buy in, Evening up, Liquidation

Omnibus account - An account carried by one futures commission merchant with another futures commission merchant in which the transactions of two or more persons are combined and carried in the name of the originating broker, rather than designated separately. Related: Commission house, Futures commission merchant

Open contracts - Contracts which have been bought or sold without the transaction having been completed by subsequent sale or purchase, or by making or taking actual delivery of the financial instrument or physical commodity.

Open interest - The total number of futures contracts traded in a given commodity that have not yet been liquidated either by an offsetting futures transaction or by delivery. Related: Liquidation

Open order - An order to a broker that is good until it is canceled or executed.

Open-Outcry - The method of trading used at futures exchanges, typically involving calling out the specific details of a buy or sell order, so that the information is available to all traders.

Open-end fund - Also called a mutual fund, an investment company that stands ready to sell new shares to the public and to redeem its outstanding shares on demand at a price equal to an appropriate share of the value of its portfolio, which is computed daily at the close of the market.

Opening price - The range of prices at which the first bids and offers were made or first transaction were completed. Related: Range

Opening, the - The period at the beginning of the trading session officially designated by the exchange during which all transactions are considered made "at the opening". Related: Close, the

Operating cycle - The average time intervening between the acquisition of materials or services and the final cash realization from those acquisitions.

Operationally efficient market - Also called an internally efficient market, one in which investors can obtain transactions services that reflect the true costs associated with furnishing those services.

Opportunity costs - The difference in the performance of an actual investment and a desired investment adjusted for fixed costs and execution costs. The performance differential is a consequence of not being able to implement all desired trades.

Optimal portfolio - An efficient portfolio most preferred by an investor because its risk/reward characteristics approximate the investor's utility function. A portfolio that maximizes an investor's preferences with respect to return and risk.

Optimization approach to indexing - An approach to indexing which seeks to Optimize some objective, such as to maximize the portfolio yield, to maximize convexity, or to maximize expected total returns.

Option - The right, but not the obligation, to buy or sell an underlying futures contract.

Option premium - The option price.

Option price - Also called the option premium, the price paid by the buyer of the options contract for the right to buy or sell a security at a specified price in the future.

Option seller - Also called the option writer, the party who grants a right to trade a security at a given price in the future.

Option writer - Option seller.

Option-adjusted spread (OAS) - The spread over an issuer's spot rate curve, developed as a measure of the yield spread that can be used to convert dollar differences between theoretical value and market price.

Options contract - A contract that, in exchange for the option price, gives the option buyer the right, but not the obligation, to buy (or sell) a financial asset at the exercise price from (or to) the option seller within a specified time period, or on a specified date (expiration date).

Options contract multiple - A constant, set at $100, which when multiplied by the cash index value gives the dollar value of the stock index underlying an option. That is, dollar value of the underlying stock index = cash index value x $100 (the options contract multiple).

Options on physicals - Interest rate options written on fixed-income securities, as opposed to those written on interest rate futures contracts.

Original margin - The margin needed to cover a specific new position. Related: Margin, Security deposit (initial)

Out-of-the-Money - A put option with a strike price lower than the underlying futures price, or a call option with a strike price higher than the underlying futures price. Related: In-the-Money

Over-the-counter market (OTC) - A decentralized market (as opposed to an exchange market) where geographically dispersed dealers are linked together by telephones and computer screens.

Overlay strategy - A strategy of using futures for asset allocation by pension sponsors to avoid disrupting the activities of money managers.

Overnight repo - A repurchase agreement with a term of one day.

Overreaction hypothesis - The supposition that investors overreact to unanticipated news, resulting in exaggerated movement in stock prices followed by corrections.

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