The term nation state, while often used interchangably with the term state, refers more properly to a state in which a single nation is dominant. Over the last few centuries (and particular over the last half-century), this form of state has become more common, so that now most states are nation states. However, this has not always been so; and even today there are some states where it is questionable whether they are contain a single dominant nation. This is made more difficult by the question of what is a nation. There are many states, such as Belgium and Switzerland, with multiple linguistic, religious or ethnic groups within them, without any one being clearly dominant. However, often (and especially in the case of Switzerland) a national identity has been constructed despite these differences. A better example of a non-nation state would be the United Kingdom, which consists of the four nations England, Scotland, Northern Ireland and Wales. While people do talk of a 'British nation', it is questionable whether such an entity really exists. And although England in the past was dominant within the United Kingdom, with devolution the same can no longer be said to be clearly the case.