Imperialism, colonialism, and decolonization the colonial expansion of european states into the americas, asia, africa, and the pacific, followed by the collapse of these empires and their replacement by sovereign nation-states, is a double movement of great historical importance.
Unless the purview of the question is the historical development of each and their supposed moral justification, the main difference between colonialism and imperialism is the spelling colonialism : an authoritarian form of government which involves the removal of the sovereignty of others. Colonialism is the policy of a foreign polity seeking to extend or retain its authority over other people or territories, generally with the aim of developing or exploiting them to the benefit of the colonizing country and of helping the colonies modernize in terms defined by the colonizers, especially in economics, religion, and health.
The russian leader lenin suggested that imperialism was the highest form of capitalism, claiming that imperialism developed after colonialism, and was distinguished from colonialism by monopoly capitalism.
Robert jc young, a british historian, subscribes to the fact that imperialism is the concept while colonialism is the practice taking that into account, it can be said that colonialism is the consequence of imperialism one cannot exist without the other since colonies have to be established for an empire to flourish.
Assumptions are that colonialism and imperialism are interchangeable, however robert j c young suggests that imperialism is the concept while colonialism is the practice colonialism is based on an imperial outlook, thereby creating a consequential relationship through an empire, colonialism is established and capitalism is. Imperialism often produces colonialism, and colonialism is an integral part of imperialism definitionally, imperialism means a policy of extending a country's power and influence through diplomacy or military force. Colonial resistance and rebellion forced europeans to develop new strategies of rule the british granted self-government to canada, australia, and new zealand nineteenth-century empires established carefully codified racial hierarchies.
Colonialism and imperialism are often used interchangeably, but they are two different words having different meaning as both colonialism and imperialism means political and economic domination of the other, scholars often find it hard to differentiate the two though both the words underline.