In this context, a(x) represents a specific function that we want to find the derivative for. It's typically written as "f(x)" but can be represented by any letter followed by "(x)".
Related terms
Function: A mathematical rule that assigns each input value (x) to exactly one output value (a). In this case, our function is represented by "a(x)".
Dependent Variable: The variable (in this case, 'a') whose value depends on another variable ('x').
Independent Variable: The variable ('x') whose value determines the value of the dependent variable ('a').