Final answer:
Dispersion is the term that describes the spread of people or things across space, which can include the movement of populations due to various factors such as natural disasters, political issues, and seeking resources.
Step-by-step explanation:
The term that refers to the spread of people or things across space is dispersion. While migration involves the movement and often permanent relocation of people, dispersion describes the more general spread over a space which can be applicable to both living organisms and non-living entities. For example, the spread of a religion like Islam through both expansion diffusion (contagious and hierarchical) and relocation diffusion showcases dispersion across populations.
Movement can take various forms such as immigration (coming into an area), emigration (leaving an area), and even environment-driven displacement due to natural disasters. Each of these forms encapsulates the various facets and reasons behind the movement or spread of populations, whether it is for finding resources, seeking safety, or pursuing better living conditions. Ultimately, migration is a type of movement that indirectly contributes to the dispersion of ideas, cultures, and people across the globe.