Can I assign multiple expenditure type classes to an expenditure type?

Yes. For example, an expenditure with the expenditure type Materials can have the expenditure type class Supplier Invoice if it originated in Oracle Fusion Payables, and the expenditure type class Inventory if it originated in Oracle Fusion Inventory.

This allows you to use a single expenditure type to classify as many costs as you need. You can use the same expenditure type for expenditures with different origins, and therefore different accounting, that should otherwise be grouped together for costing, budgeting, or summarization purposes.