Vendor vs. supplier

Louise asked, "What is the difference between a vendor and a supplier?"

Both of these words can be used to talk about a person or business that sells a particular type of product, as in these examples:

• They are the biggest supplier of books in the area.
• There were many more software vendors at the trade show this year.

However, vendor can also be used to refer to a person selling something from a cart on the street, such as hot dogs or sunglasses:

• The hotdog vendor on the corner sells soda and pretzels, too.

Supplier would be very odd in this context.