That is used in mathematical or logical expressions to represent a variable quantity .
用在数学或者逻辑表达式里代表一个可变量的符号。
A symbol that is used in mathematical or logical expressions to represent a variable quantity.
用在数学或者逻辑表达式里代表一个可变量的符号。
The mathematical mean of the physical quantity has multiple expressions forms, including arithmetical mean and geometric mean, etc.
物理量的数学平均值有算术平均值和几何平均值等多种表达形式，这些数学平均值所表达的物理含义是不同的。
When expressions of measurement, amount and quantity are used as adjectives, they are normally singular.
当度量单位，数量等被用作形容词时，通常用单数形式。如。
When expressions of measurement, amount and quantity are used as adjectives, they are normally singular.
当度量单位，数量等被用作形容词时，通常用单数形式。如。
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