docs/handbook/guidelines/c_cpp.md

@@ -99,7 +99,19 @@ int64_t size() const {...}
 
 ### Enums
 
-- Labels in enums should be in all capitals.
+- Enum type names should avoid being confused with related structs or classes.
+
+  Recommended suffixes include:
+
+  - `Type` & `Mode` for discrete values.
+  - `Flag` & `Mask` for values which are treated as bit-masks.
+
+  However these are guidelines which may be applied selectively.
+  Terms such as `Direction`, `Stage`, `Code` & `Method` (among others) are
+  sufficiently descriptive not to require one of the recommended suffixes.
+
+- C style enum labels in enums should be in all capitals.
+- C++ style enums labels which use `enum class` should use pascal-case.
 - Enums used in DNA files should have explicit values assigned.
 
 ### Function arguments