Is Britain a country, or four?

The word "country" is a bit nebulous. To the rest of the world, functionally, Britain acts as one country with a unified foreign policy and a single face and voice presented to the outside world. How they think of themselves, as 4 countries within the United Kingdom, or even counting their independent commonwealths like Australia and Canada, which are seen as separate countries by the outside world, well, that's up to them.

The terminology isn't all that important. Israel is called a "state". In the end, what matters in global politics is how the foreign policy is presented. The United States, for example, has vast differences of opinion regionally and sometimes down to the level of independent States. Our domestic policy is greatly divided and differs markedly in different States. But the President is the sole voice of foreign policy for all 300+ million of us. There is a great deal of disagreement in foreign policy and it is vigorously debated within the government, but government officials on official business abroad will not question the President on foreign policy matters. If they do, it is seen as stepping way out of bounds. So we speak with one voice and are functionally one nation. (There are other reasons we are functionally one nation, since our central government is pretty powerful, but the foreign policy part I think is the most important.)

UK means united demons they like to torture other countries and steal their riches and make them slave and still call themselves Gentleman this must be gentle-demon currently they don't hold power over the world like they did years before which is good

britain is not a country,but the united kingdom of great britain and northern ireland is,btw ireland is not part of the u.k.

The United Kingdom is a unitary political state that is comprised of four different nations, England, Scotland, Wales, and Northern Ireland. It used to be very centralised in London, but in the last decade, the constituent nations have gotten alot more power through devolution of powers from Westminster, the UK parliament.

Great Britain or Britain refers to the island and only contains England, Scotland and Wales.

The country made of 4 states (they are countries in their own right) you are thinking of is United Kingdom (which include northern ireland)

They are countries within a country. "Country" doesn't necessarily mean having an independent government. All the word "country" really means is (something like) a well defined territory associated with a particular national group. As you can see, under this definition, Wales, Scotland, England and Northern Ireland are all countries, as is the UK.

As it happens, Scotland, Wales and Northern Ireland all have their own governments, which are subordinate to the British government (they're a bit like state legislatures in the US).

In Wales, there's the Welsh Assembly in Cardiff, whose leader (the First Minister of Wales) is Alun Michael.

In Northern Ireland there's the Northern Ireland Assembly in Belfast, whose leader (the First Minister of Northern Ireland) is Peter Robinson.

In Scotland there's the Scottish Parliament in Edinburgh, whose leader (the First Minister of Scotland) is Alex Salmond. Unlike the other two, Scotland also has its own separate legal system (although there are laws in every part of the UK that don't apply to the whole).

England has no parliament of assembly of its own, but the government of the United Kingdom is located in England. This government, whose leader (the Prime Minister of the United Kingdom) is called David Cameron, has overall control over the United Kingdom as a whole.

The overall head of State of the United Kingdom (along with Canada, Australia, and many other countries) is Queen Elizabeth II. But her role is mainly ceremonial.

---
A couple of people have said that Wales is a Principality, but this is misleading. The Principality of Wales was something that existed centuries ago. There is no such thing any more, and the term has no constitutional meaning. In any case, it's worth adding that a principality can also be a country. The terms are not mutually exclusive. The question's irrelevant in the case of Wales though.

Great Britain is the 'larger' island. Formed of England, Scotland and Wales. The UK is the same island, but also includes Northern Ireland.

Ireland is a separate country. Do not go up to someone from Ireland and tell them they're from Britain/UK. They will NOT be happy.

Technically Wales is a principality, and England and Scotland are Kingdoms.

If you want to refer to both islands, (so Great Britain - where England, Wales and Scotland are) AND the smaller Ireland containing Ireland and Northern Island, plus all our smaller outlying island such as Isle of Wight and the Channel Islands, then you can refer to them as the British Isles. Ireland is part of the British Isles.

the four together are called the UK and its just northern ireland not all of it

Great Britain is 2 countries (England and Scotland) and 1 principality (Wales)
The United Kingdom is the above plus a province (Ulster - Northern Ireland)

Scotland, Wales and Ulster all have their own state governments above them is the national government in London.

There are no presidents in the UK, Scotland, Wales and Ulster all have 'first ministers' the UK as a whole has a Prime Minister - above them all is the Queen

britain is a country
england, wales, etc are more like the the states that make up the country