Rural settlement patterns on the island of Java conform in general type to the dominant mode throughout the rest of monsoon Asia: a nucleated residential unit surrounded by the lands cultivated by the residents, forming a community with political, economic, and religious dimensions. The dominant form of agriculture depends upon irrigated lands planted primarily with rice. In upland areas, where the topography has limited the spread of the irrigated land, the residential units are relatively small and isolated, and a characteristic village organization has developed in which the daily patterns of interaction can encompass the entire village. The much larger part of Java's population, however, lives in lowland areas where gentle, even gradients, plentiful sources of water, and the seasonal rains have permitted the establishment of widespread systems of irrigation. Here the residential units have expanded and coalesced into large blocks and strips of several square miles, alternating with large uninterrupted areas of irrigated land. Under these conditions, village units have expanded far beyond the daily interaction group, and vaguely denned neighborhoods (barisan or lingkungan) have developed within which most of the daily patterns of mutual interest and aid take place. Within the area studied, the average population of the lowland rural village is roughly 600, with a range from 200 to 2000. The average area encompassed by each village is roughly a quarter square mile, with a range approximately proportional to the population.