One: Mathematically, it refers to the frequently changing quantity, which is a Greek letter transliterated as "Delta". δ is the quantity of a basic discriminant in a quadratic equation discriminant in mathematics. For the unary quadratic equation ax 2+bx+c, there is △ = b 2-4ac. We can judge the number of quadratic equations with one variable by the value of △. When △ ; X has two different real roots at 0. After the judgment is completed, if the equation has roots and belongs to two or three situations, the root of the equation can be found according to the formula: x = {-b √ (b 2-4ac)}/2a. 2. Geometric representation of "triangle" 3. Physics In physics, the formula for calculating the heat absorbed or released by an object when it absorbs or emits heat is Q=cm△t(c stands for the specific heat capacity of the substance, m stands for the mass △t stands for the temperature change, and the temperature rise is t 1-t0-T 1). △t can also represent time difference. Four: Chemistry means "heating" in chemical equations and is usually used in chemical reaction equations.