Scotland is not a country. It is a nation within the country of United Kingdom. Northern Ireland, Wales and England are the other nations that comprise the United Kingdom.
A nation is a group of people who share one or commonalities of heritage, culture, traditions or language. Although the people of Scotland meet the criteria to be a nation, they lack the autonomy of government to declare themselves a country. The United Kingdom's parliament has governance over many of Scotland's affairs. In 2014, Scotland held a historic vote to secede from the United Kingdom following centuries of Scottish descent from British rule. The notion was defeated by a slim margin, however, and Scotland remains part of the United Kingdom.