Elements in a hierarchy are ordered according to their importance. Settlements can be put in order of importance using a range of factors that include size, population and services.
Services are facilities provided for people and include shops, schools, hospitals, libraries, post offices and churches. The number and range of services provided in a settlement increases with settlement size. Larger settlements have bigger populations who require more services. As a settlement becomes more important, a larger amount of people are willing to travel further to that settlement further increasing the services found there.
A settlement like Gracehill which has a population of less than 1000 is called a hamlet. In hamlets there may be no services at all - perhaps just a public telephone.
A village like Kilrea has between 1 000 and 2 250 inhabitants. Villages have a small number of services such as a church, Post Office, Public House, a small shop for daily goods, perhaps a small primary school and a village hall.
A small town might have a town hall, doctor, several churches, cafes and restaurants, a small secondary school, small railway or bus station, and several shops. Randalstown is a small town and has a population of between 4 500 and 10 000 people.
A large town like Omagh might have several shopping areas or arcades, a railway and/or bus station, hotels, banks, a hospital and even a local football team. Large towns have a population of between 18 000 and 75 000.
Belfast Metropolitan Urban Area is the largest urban area in Northern Ireland with a population of approximately 580 000.
A city like Belfast will have a large range of services that include hospitals, railway stations, several large shopping complexes, a cathedral, specialist shops, universities, theatres and several sports' teams.
Settlements can be put in order of importance using a range of factors that include size, population and services.