It seems there might be some confusion in your question regarding what both the Roman Catholic Church and the Eastern Orthodox Church permit. Both churches permit the use of icons, which are religious images.
To clarify the usage during worship:
- The Roman Catholic Church primarily uses Latin for its traditional worship services (although vernacular languages are also widely used now).
- The Eastern Orthodox Church primarily uses Greek or Slavic (e.g., Russian) depending on the specific Orthodox tradition for their services.
So, completing your sentences, you could say:
Both the Roman Catholic Church and the Eastern Orthodox Church permit the use of icons. However, the Roman Catholic Church uses Latin for worship services while the Eastern Orthodox Church uses Greek or Russian (depending on the specific tradition).