What is a cooking substitute for an egg?

Substituting eggs is tricky because eggs play different functions in foods: emulsifying, enriching, adding structure when baking. Consider the recipe and whether the yolk or the whites are more important. If baking a cake, it's probably the white (for structure), and you may need to add additional baking powder or a different leavening. For brownies and cookies it's probably the yolk that is important for richness or emulsion, and possible substitutes might range from additional oil or butter to yogurt, applesauce or bananas. The link attached below provides further information.