The most common form today is a residential or public garden, but the term "garden" has traditionally been a more general one. Zoos, which display wild animals in simulated natural habitats, were formerly called zoological gardens. Western gardens are almost universally based on plants, with "garden", which etymologically implies "enclosure", often signifying a shortened form of botanical garden. Some traditional types of eastern gardens, such as Zen gardens, however, use plants sparsely or not at all. Landscape gardens, on the other hand, such as the English landscape gardens first developed in the 18th century, may omit flowers altogether.