‘British Isles, Great Britain and United Kingdom’ – On the surface it might mean the same; in reality each word refer a different entity geographically and politically. A simple explanation related to Britain will lend more clarity to the above terms.
British Isles – The group of islands that include Great Britain, Ireland, Isle of Man, Guernsey, Jersey and group of smaller islands present in the Atlantic Ocean and off the coast of Continental Europe. The catalogue of British Isles includes more than 6,000 islands
Great Britain – The largest island of the British Isles archipelago constituting the nations England, Scotland and Wales.
Ireland – The second largest island of the British Isles Archipelago that lies to the west of Great Britain.
United Kingdom – Officially referred as United Kingdom of Great Britain and Northern Ireland is a constitutional entity that encloses the Island of Great Britain, small islands near to Great Britain and the northern-eastern part of Ireland.
In much simple terms, UK constitutes the four nations namely England, Wales, Scotland and Northern Ireland.
UK’s legal jurisdictions splits into three separate ones; England & Wales, Scotland and Northern Ireland.
Ireland – Politically, Ireland refers to the Republic of Ireland that occupies a major part of geographical Ireland. The sovereign republic is referred as “The Republic of Ireland”.