The term hydroponics is used to describe many different types of systems for growing plants without soil. Among the most common are:

1 water culture, aquaculture, or nutriculture - a system in which the plant roots are immersed in water containing dissolved nutrients
2aggregate culture -  in which a material such as sand, gravel, or marbles supports the plant roots
3aeroponics -  in which the plant roots hang in the air and are misted regularly with a nutrient solution
4continuous flow systems -  in which the nutrient solution flows constantly over the plant roots. This system is the one most commonly used for commercial production.