An association between two tables in which one record in either table can relate to many records in the other table. To establish a many-to-many relationship, you need to create a third (junction) table and add the primary key fields from each of the other two tables to this table. For example, if you have a Products table and an Orders table, an order can include more than one product, and a product can be included in more than one order. You must create a junction table that has a one-to-many relationship with the Products table and a one-to-many relationship with the Orders table.