In North America and Australasia today, a yard can be any part of a property surrounding or associated with a house or other residential structure, usually (although not necessarily) separate from a garden (where plant maintenance is more formalized). A yard will typically consist mostly of lawn or play area. The yard in front of a house is referred to as a front yard, the area at the rear is known as a backyard. Backyards are generally more private and are thus a more common location for recreation. Yard size varies with population density. In urban centres, many houses have very small or even no yards at all. In the suburbs, yards are generally much larger and have room for such amenities as a patio, a playplace for children, or a swimming pool.