A banyan is a fig that starts its life as an epiphyte when its seeds germinate in the cracks and crevices on a host tree (or on structures like buildings and bridges). "Banyan" often refers specifically to the species Ficus benghalensis, though the term has been generalized to include all figs that share a unique life cycle. The seeds of banyans are dispersed by fruit-eating birds. The seeds germinate and send down roots towards the ground, and may envelope part of the host tree of building structure with their roots, giving them the casual name of strangler fig. The "strangling" growth habit is found in number of tropical forest species, particularly of the genus Ficus, that compete for light. Any Ficus species showing this habit may be termed a strangler fig. It is also called ficus indica.
Older banyan trees are characterized by their aerial prop roots which grow into thick woody trunks which, with age, can become indistinguishable from the main trunk. Old trees can spread out laterally using these prop roots to cover a wide area. The largest such tree is now found in Kolkata in India. One famous banyan tree was planted in 1873 in Lahaina's Courthouse Square in Hawai'i, and has grown to now cover two-thirds of an acre.
Like other Fig species (which includes the common edible fig Ficus carica), banyans have a unique fruit structures and are dependent on fig wasps for reproduction.