Diffusion is the spread of ideas, goods, or technologies from one place to another. It can happen through trade, travel, migration, or communication. Diffusion occurs in both ancient and modern societies.

For instance, inventions such as paper moved from China to other regions, and religions like Christianity and Islam spread across continents. Clothing styles, foods, and tools have also spread through diffusion. These changes can be traced across different regions.

Diffusion is studied in geography and history using maps, records, and artifacts. It helps show how cultures and technologies spread over time.