UK vs United Kingdom

UK

United Kingdom

name
  • A kingdom and sovereign state in Western Europe comprising the four countries of England, Scotland and Wales in the island of Great Britain, and Northern Ireland in the island of Ireland. Since 1922. 

  • The Kingdom of Great Britain (1707–1801). 

  • Kingdom consisting of several constituencies, actual, historical, or hypothetical. 

  • The United Kingdom of Great Britain and Ireland (1801–1922). 

How often have the words UK and United Kingdom occurred in a corpus of books? (source: Google Ngram Viewer )