This document provides an introduction to the equation of continuity in fluid dynamics. It begins with definitions of incompressible, laminar and viscous fluid motion. It then introduces the equation of continuity, which states that the mass flow rate is constant for incompressible fluid flow in a closed system. The equation is derived and formulated as ρ1V1A1 = ρ2V2A2, where ρ is density, V is velocity, and A is cross-sectional area. Examples are given of how velocity must increase as area decreases to satisfy the equation. In conclusion, the continuity equation dictates that velocity is inversely proportional to cross-sectional area for incompressible fluid flow through a pipe.