Interpretatio graeca (Latin, "Greek translation") or "interpretation by means of Greek [models]" is a discourse used to interpret or attempt to understand the mythology and religion of other cultures; a comparative methodology using ancient Greek religious concepts and practices, deities, and myths, equivalencies, and shared characteristics.
The phrase may describe Greek efforts to explain others' beliefs and myths, as when Herodotus describes Egyptian religion in terms of perceived Greek analogues, or when Dionysius of Halicarnassus and Plutarch document Roman cults, temples, and practices under the names of equivalent Greek deities. Interpretatio graeca may also describe non-Greeks' interpretation of their own belief systems by comparison or assimilation with Greek models, as when Romans adapt Greek myths and iconography under the names of their own gods.
Interpretatio romana is comparative discourse in reference to ancient Roman religion and myth, as in the formation of a distinctive Gallo-Roman religion. Both the Romans and the Gauls reinterpreted Gallic religious traditions in relation to Roman models, particularly Imperial cult.
The great achievement of polytheism is the articulation of a common semantic universe. ... The meaning of a deity is his or her specific character as it unfolded in myths, hymns, rites, and so on. This character makes a deity comparable to other deities with similar traits. The similarity of gods makes their names mutually translatable. ... The practice of translating the names of the gods created a concept of similarity and produced the idea or conviction that the gods are international.
Pliny the Elder expressed the "translatability" of deities as "different names to different peoples" (nomina alia aliis gentibus). This capacity made possible the religious syncretism of the Hellenistic era and the pre-Christian Roman Empire.