The person or company that supplies a customer with the largest quantity of goods or services compared to all other suppliers.
This is a supplier that is specified as the primary source for a particular item in the system. The 'main supplier' is usually the supplier that is used first when creating a purchase order for the item. In SAP Business One, you can specify such a primary vendor for an item by going to the "Purchasing" tab in the item's master data and selecting the appropriate vendor from the "Primary Vendor" dropdown menu.
It is important to note as a particular item in SAP Business One can have multiple suppliers, but only one of them can be set as the main supplier.