- 
DerivativeThe instantaneous rate of change of a function f (x) at a particular point x0, denoted f'(x0) or  (x0).  The formal definition is the following limit: (x0).  The formal definition is the following limit:f'(x0) =   
 
- 
Derivative FunctionA function f'(x) taking on the value of the derivative of f (x) at each number x. 
- 
Difference QuotientFor a function f, and any two points x0 and x in its domain, the quotient:  
 
- 
DifferentiableA function f is differentiable at a point (x0) if it has a well-defined derivative at that point. It is simply differentiable if it is differentiable at every point in its domain. 
- 
Secant LineA line through two distinct points on the graph of a function. 
- 
Tangent LineA line through a point (x, f (x)) on a graph that has slope equal to the derivative of the function f at x. A limit of secant lines to the graph of a function as two contact points approach one another. 
 
         
   
                     
                     
                    