The species of mappings central to conceptual metaphor theory. Mappings of this kind persist in long-term memory and serve to structure one conceptual domain (2), the target domain, in terms of another domain, the source domain. Cross domain mappings are held to provide one of the key ways in which the conceptual system is organized.

According to conceptual metaphor theory, it is due to the existence of cross-domain mappings that we can think and talk about one domain, for instance the domain of quantity in terms of another domain, for instance the domain of verticality. This is evidenced by an example such as She got a really high mark in the test. In this example, high relates not literally to physical height but to a good mark. That is, we understand quantity in terms of height due to a conventional association between the two domains facilitated by long-term cross-domain mappings projecting structure from the source domain onto the target domain. In practice cross-domain mappings are conceived of as a stable relationship holding between sets of concepts belonging to two distinct domains.

A set of cross-domain mappings holding between two distinct conceptual domains is referred to as a conceptual metaphor.