Invention, innovation, and cultural diffusion are all ways in which societies change. To most anthropologists, innovation and invention are similar things whereas cultural diffusion is relatively different.
An invention, in anthropological terms, is the creation or discovery of something that is completely new. For example, in prehistoric times, people invented the atlatl, or spear-thrower. This new device gave them more leverage and allowed them to throw spears much farther. Since it had not existed before, it was an invention (sometimes called a “primary innovation”). An innovation, by comparison, occurs when an existing idea or object is taken and modified for a new use. For example, let us imagine that a society has invented the wheel and axle and has been using them for carts to carry farm products to market. If the society then thinks to use the wheel and axle for a war chariot, it is an innovation because the society has taken an existing idea and used it in a novel way.
While invention and innovation are similar, cultural diffusion is rather different. Cultural diffusion occurs when a society “borrows” an idea from another society. For example, paper-making is believed to have started with the Chinese. It was then borrowed by the Arabs who, in turn, transmitted it to Europe. These cultures changed as paper came into use, but neither the Arabs nor the Europeans actually invented paper.
Thus, invention, innovation, and cultural diffusion are all ways in which cultural change can occur.