In biology, commensalism is defined as a symbiotic relationship between two organisms in which one organism benefits from the other without harming it. In plant commensalism, one plant typically lives on or near another plant (the host) and derives some benefit from the association, such as increased access to sunlight or water. The host plant is usually not harmed by the association. A classic example of plant commensalism is the relationship between epiphytic plants (plants that grow on other plants) and their hosts. Epiphytes often have shallow root systems that do not penetrate deeply into the soil; instead, they rely on their host plants for support. Many epiphytes also lack leaves, or have small leaves, which helps them minimize competition with their host plants for sunlight. In exchange for these benefits, epiphytes typically provide their hosts with nutrients derived from decomposing organic matter that collects on their leaves and stems.