An 'empire' is a group of countries ruled over by a single monarch or ruling power. An empire doesn't need an 'emperor'.
The British Empire comprised Britain, the 'mother country', and the colonies, countries ruled to some degree by and from Britain.
The British began to establish overseas colonies in the 16th century. By 1783 Britain had a large empire, with colonies in America and the West Indies.
This 'first British Empire' came to an end after the American Revolution.
However, in the 19th century, the British built a second worldwide empire, based on British sea-power, India, and huge conquests in Africa.
Subject Knowledge: The First Empire
In 1497, only five years after Christopher Columbus sailed to the West India, the Italian explorer John Cabot, financed by English merchants, discovered new lands in Canada.
In 1585, Sir Walter Raleigh organised a small settlement at Roanoke in Virginia, but it failed.
In 1607, Captain John Smith founded a permanent colony at Jamestown in Virginia.
After 1612, the East India Company began to build up a small empire of trading posts in India.
The first successful English colonies in the West Indies were founded in the 1620s. The settlers set up sugar and tobacco plantations, and used slave labour.
In the 18th century, Britain fought a number of wars against France, taking over colonies established by the French.
Victories by Robert Clive, especially the Battle of Plassey in 1757, drove out the French and established British control in India.
During the Seven Years' War (1756-1763) the British won Canada from the French with a notable victory coming from General James Wolfe's capture of Quebec in 1759.
By 1783, Britain had established an empire which comprised: colonies in Canada, America and the West Indies; trading posts in India, and naval bases in the Mediterranean (Gibraltar and Minorca).
But Britain's defeat in the American War of Independence (1775-1783) meant the loss of the American colonies and the end of the 'first British Empire'.
Subject Knowledge: 1783-1924, The Age of Empire
In the century 1815-1914, 10 million square miles of territory and 400 million people were added to the British Empire.
By the British Empire Exhibition of 1924 Britain was the 'Mother Country' of a worldwide empire which covered a fifth of the land in the world.