Colonization of the 16th-18th centuries consisted of organized groups of people under the authority of a state arriving in a land without a central government, seizing territory for a new settlement, carrying on their own ways with an intent to do so indefinitely, and extend the reach of the monopoly of force of their mother state over the surrounds.
Immigration of the 19th-21st centuries consists of individuals or small groups outside of the context of a state-sanctioned expedition being accepted in by the authority of the native state already exercising a monopoly of force over the area, and in doing so, renouncing other loyalties either implicitly or explicitly, arriving in settlements already dominated by the majority ethnicity, assimilating, and participating in upholding the social contract between government and citizens.
You will note, I hope, that colonization necessarily excludes the prospect of the colonizers joining the settlements of the pre-existing majority ethnicity of the land, that colonizers set up a state or an extension of a state that is non-native, explicitly refuse the prospect of assimilating into the majority ethnicity of the area (though to be entirely fair, there were few places with a true ‘majority’ ethnicity that managed to be colonized - that’s another discussion entirely, though), and that colonizers do so in the form of organized groups seeking a collective gain for the group, not individuals and their families or small social circles seeking individual gain.
Colonization of the 16th-18th centuries consisted of organized groups of people under the authority of a state arriving in a land without a central government, seizing territory for a new settlement, carrying on their own ways with an intent to do so indefinitely, and extend the reach of the monopoly of force of their mother state over the surrounds.
Immigration of the 19th-21st centuries consists of individuals or small groups outside of the context of a state-sanctioned expedition being accepted in by the authority of the native state already exercising a monopoly of force over the area, and in doing so, renouncing other loyalties either implicitly or explicitly, arriving in settlements already dominated by the majority ethnicity, assimilating, and participating in upholding the social contract between government and citizens.
You will note, I hope, that colonization necessarily excludes the prospect of the colonizers joining the settlements of the pre-existing majority ethnicity of the land, that colonizers set up a state or an extension of a state that is non-native, explicitly refuse the prospect of assimilating into the majority ethnicity of the area (though to be entirely fair, there were few places with a true ‘majority’ ethnicity that managed to be colonized - that’s another discussion entirely, though), and that colonizers do so in the form of organized groups seeking a collective gain for the group, not individuals and their families or small social circles seeking individual gain.