What term describes the act of coming into a certain region?

The term that describes the act of coming into a certain region is immigration. Immigration specifically refers to the process by which individuals move into a country or region from another place, typically with the intent of settling there. This can involve various legal processes depending on the laws of the receiving country.

Migration, while related, is a broader term that encompasses both the movement of people into and out of a region. It does not differentiate between arriving in a new place and leaving one, which makes it less specific than immigration. Emigration, on the other hand, refers to the act of leaving one's country to settle in another, thus focusing on the departure rather than the arrival. Relocation involves moving from one place to another but does not inherently imply crossing borders or changing countries, making it more general.

Therefore, immigration is the term that accurately captures the action of entering a new region with the intention of living there.