Function of a real variable
![A function of a real variable](/Images/godic/202502/06/Real_function_of_one_variable.svg0740.png")
![Limit of a real function of a real variable.](/Images/godic/202502/06/Limit_of_a_real_function_of_a_real_variable.svg0740.png")
![Space curve in 3d. The position vector r is parametrized by a scalar t. At r = a the red line is the tangent to the curve, and the blue plane is normal to the curve.](/Images/godic/202502/06/Space_curve.svg0740.png")
![Kinematic quantities of a classical particle: mass m, position r, velocity v, acceleration a.](/Images/godic/202502/06/Kinematics.svg0740.png")
In mathematical analysis, and applications in geometry, applied mathematics, engineering, and natural sciences, a function of a real variable is a function whose domain is the real numbers ℝ, more specifically the subset of ℝ for which the function is defined.