多變的 定義
In mathematics, a variable is a symbol used to represent an arbitrary element that can change or that may take on different values. Variables may also refer to a letter, symbol, or snippet of words or text, representing such a quantity. In addition to numbers, variables are commonly used to represent vectors, matrices and functions.
使用變量進行代數計算，就好像它們是明確的數字一樣，可以在一次計算中解決一系列問題。一個典型的例子是二次公式，它允許人們通過簡單地替換給定equation的係數的數值來求解每個二次方程對於代表它們的變量。
In mathematical logic, a variable is either a symbol representing an unspecified term of the theory, or a basic object of the theory, which is manipulated without referring to its possible intuitive interpretation.
來源
“Variable (Mathematics).” Wikipedia, Wikimedia Foundation, 4 Mar. 2020, en.wikipedia.org/wiki/Variable_(mathematics).