X: Glossary Terms

X

XGBoostStocksCrypto

A widely used optimized gradient-boosting implementation with regularization and engineering features for tabular prediction tasks.

XDStocksCrypto

XD is the quotation marker showing that a security is trading ex-dividend, meaning a buyer at the current price is not entitled to the dividend that has already been declared. The flag applies from the ex-dividend date, which the exchange sets relative to the record date, and the opening price is normally adjusted downward by roughly the dividend amount. Related markers include XR for ex-rights and XC for ex-capitalisation.

X-efficiencyStocks

X-efficiency measures how close a firm comes to producing its output at the lowest cost its technology allows, given the inputs it buys. Harvey Leibenstein introduced the idea to explain why firms facing weak competitive pressure operate with organizational slack: effort, coordination and motivation fall short even though no input price has changed. The shortfall, called X-inefficiency, is distinct from allocative inefficiency, which concerns choosing the wrong mix of inputs or outputs.

XetraStocks

Xetra is the electronic trading platform operated by Deutsche Boerse and the main venue for German equities, exchange-traded funds and other listed instruments. It runs a central limit order book with continuous matching between an opening and a closing auction, plus intraday auctions, and designated sponsors quote two-sided prices in less liquid securities to support execution. Reference prices used for the German equity indices are struck on it, and several other European exchanges license the system to operate their own markets.

XRTStocksCrypto

A designation appended to a stock's ticker to show that it is trading ex-rights, meaning a buyer at the current price no longer receives the subscription rights recently distributed to holders. It belongs to the same family of tape suffixes as XD for ex-dividend and XW for ex-warrants. The share price typically adjusts downward when the marker appears, because the value of the rights has separated from the share and now trades on its own.

XenocurrencyStocksFutures

A currency held, traded or used for settlement outside the country that issued it, such as dollars deposited with a bank in Europe or Asia. Balances of this kind sit beyond the issuing central bank's domestic banking regulations, which is why a large offshore market in them developed. The term is used less often than the older prefix convention, where eurodollar, euroyen and similar labels describe the same idea regardless of where the account is actually held.