What is the difference between 'Complete' and 'Complementary'?

Complete: nutritionally complete, providing all the nutrients in the amounts and proportions the pet needs.

Complementary: These foods are designed to be a part of the diet; however they do not meet the known nutritional requirements when fed alone so they must be fed along with an additional food type such as mixer biscuits in the case of the dog, or hay, in the case of rabbits. All complementary foods are labelled as such with appropriate feeding guidelines.