What is the Difference Between Similar But Different Things, Terms, and Objects

What is the Difference between Hydrology, Hydraulics and Pneumatics

Who is unaware about power of water and air? The need is just to handle and utilize these blessings of nature in useful and precise ways. Hydrology, Hydraulics and Pneumatics are the braches of science and technology that guide us about the proper utilization of water, air and gases.