ALTHOUGH the European Single Currency - the euro - has replaced a dozen European currencies at the start of 2002, it has been with us longer than that.

The euro has been in use since January 1, 1999, on foreign exchange markets and between banks and large companies. Eleven European countries have had a long-term commitment to scrapping their traditional currencies and trading exclusively in the euro instead. A twelfth - Greece - committed later.

Those 12 nations now constitute the "euro zone". They are Austria, Belgium, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, the Netherlands, Portugal and Spain.

Well known currencies - ranging from the French franc to the Spanish peseta - have effectively been consigned to history, although cash transactions in both the euro and the outgoing national currency will still be allowed for up to two months in some countries.

Paving the way for the introduction of the euro, which is part of European Monetary Union, has been a massive undertaking. A total of 14.5 billion banknotes have been printed and 56 million coins struck.

Individual countries have been allowed to include their own national motifs in their euro designs. The whole system works in a similar way to the monetary system of the United States, in which the federation of 50 states all use the dollar and share a common interest rate.

In the case of the euro, the single interest rate is set by the European Central Bank.

Non-cash transactions - such as bank transfers and cheques - previously conducted in the national currencies of the euro zone nations, ceased from December 31 and must now be carried out exclusively using the euro.

Euro notes - introduced on January 1 - are in different colours and sizes and are easily identifiable. Coins come in eight denominations, ranging from one cent to two euro.

Although the UK has not entered the single currency system, it is not immune from the effects of its introduction. It has already had major implications for business and will affect British holidaymakers travelling within "euroland" from now on.

Purchasing your sangria in Spain or champagne in France will require payment in euro. Hopping on a tram in Amsterdam or boarding a ferryboat between the Greek islands will be the same. The people and the climates may be different but they will be unified through a common currency.

As an outsider in this financial and economic revolution, the UK will find that the exchange rate between its traditional sterling and the euro will fluctuate, as it does against the US dollar or the Japanese yen.

Several British high street name stores and retailers will accept the new currency. They include Marks & Spencer, WH Smith, Dixons and Body Shop. You can opt to be billed in euros by companies such as BT, British Gas and General Accident. Even the Inland Revenue is willing to take tax payments in euros.

Among issues that have had to be addressed by British businesses when dealing with euro zone nations have been the need to invoice in euros, rather than the old currencies, and ensuring that any cheques from the euro zone countries are in euros.

Even something as basic as your computer keyboard needs to be looked at: has it got a euro symbol key? It will probably need one.