Syncretism refers to the combining of different forms of belief or practice.

// As a scholar of religion, Laila is especially interested in the syncretism of Manichaeism, which was influenced by Christianity, Buddhism, and Zoroastrianism.

See the entry >

"Explore the archaeological wonders of Chavín de Huantar, where history comes alive. This village, steeped in cultural richness, provides a journey into Peru's ancient past. 'The village of Chavín de Huántar is an example of how tourism can foster syncretism between religious traditions and ancestral cultural elements, generating experiences with a positive impact for the population and improving the quality of life of its residents,' said the UNWTO [United Nations World Tourism Organization]." — Laura Begley Bloom, Forbes, 26 Nov. 2023

The ancient Greeks used the term synkrētismos to refer to Cretan cities allied in opposition to a common enemy. In the early 17th century, English speakers adopted the term in the anglicized form syncretism to refer to the union of different religious beliefs. Three centuries later, lexicographers of the 1909 edition of Webster's New International Dictionary of the English Language added a new definition of syncretism ("the union or fusion into one or two or more originally different inflectional forms, as of two cases"), but this specialized sense is rarely encountered outside of the field of linguistics. Some related terms that you are more likely to encounter are syncretize ("to attempt to unite and harmonize"), syncretist ("one who advocates syncretism"), and syncretic and syncretistic ("characterized or brought about by syncretism").