also vary within a sport. In men's association football, for instance, England, Scotland, Wales, and Northern Ireland compete as separate nations at the FIFA World Cup but join together as the Great Britain Olympic football team ("Team GB") for the Olympics. Rugby union players from both Ireland and Great Britain play for British and Irish Lions representing the four "Home Unions" of England, Ireland, Scotland and Wales. Great Britain is sometimes used to mean United Kingdom. For example, at the Olympic Games, the team called "Great Britain" marches under the letter "G" in the Parade of Nations and represents Great Britain and Northern Ireland. However, since athletes from Northern Ireland have entitlement to dual nationality, they have the choice of participating in either the Great Britain team or the Republic of Ireland team. Conversely, at the Universiade, the team marches under the full name "United Kingdom of Great Britain and Northern Ireland" under the letter "U" in the Parade of Nations. In the majority of individual sports (e.g. tennis and athletics), at the international level competitors are identified as GB if they are from Great Britain or Northern Ireland. A small number of sports (e.g. golf, darts, snooker) identify participants as representing their constituent country. In the Commonwealth Games, England, Northern Ireland, Scotland and Wales each compete as separate nations, as do each of the three Crown Dependencies (Ireland is not part of the Commonwealth and is not eligible to participate). Visual guide Below is a visual reference guide to some of the main concepts and territories described in this article: Terminology in detail Britain is a political and geographic term which can refer to the United Kingdom of Great Britain and Northern Ireland, or the island of Great Britain. Great Britain is the largest island in Europe and the political union of three nations, these being: England and Wales is a political and administrative term referring to the two home countries of England and Wales, which share the same legal system. Between 1746 and 1967 the term "England" did legally include Wales. England (see also the historical Kingdom of England). Wales (see also the historical Principality of Wales). Scotland (see also the historical Kingdom of Scotland) The historical Kingdom of Great Britain is Britain for the period 1707–1801. is the Latin name for Great Britain or for the Roman province of Britain, or a poetic reference to later Britain,