Acid rain is rain or any other form of precipitation that has acidic components, such as sulfuric or nitric acids, that fall to the ground from the atmosphere. It is caused by the emission of sulfur dioxide and nitrogen oxides from power plants, factories, and vehicles, which react with water, oxygen, and other chemicals in the atmosphere to form acids.

Rain, on the other hand, is simply precipitation in the form of water droplets that fall from the sky. It can be caused by various weather conditions, such as condensation of water vapor in the atmosphere or melting of ice particles in clouds. Rainwater is naturally slightly acidic due to the presence of dissolved carbon dioxide from the atmosphere, but its pH level is usually around 5.6, which is considered slightly acidic but not harmful.

The main difference between acid rain and rain lies in their chemical composition and pH levels. Acid rain has a pH level below 5.6, making it more acidic than regular rain, which can cause harmful effects on the environment and human health.