The acquisition of additional business activities that are at the same level of the value chain in similar or different industries. This can be achieved by internal or external expansion. Because the different firms are involved in the same stage of production, horizontal integration allows them to share resources at that level. If the products offered by the companies are the same or similar, it is a merger of competitors. If all of the producers of a particular good or service in a given market were to merge, it would result in the creation of a monopoly. Also called lateral integration.