In a unary operation in a mathematical system,one element is used to yield a single result. 在數學系統中的一元運算里，一個元素往往只產生一個單一的結果。
The requested metafile operation is not supported. 不支持請求的圖元操作。
The context in which an operator symbol is used always determines whether the symbol represents a unary or binary operator. 對於這類操作符，需要根據該符號所處的上下文來確定它代表一元操作還是二元操作。
