What is difference between substitute and adulterant?

A substitute is a product that is used in place of another, often for reasons such as cost or availability, while maintaining similar characteristics or functions. An adulterant, on the other hand, is a substance that is added to another product, often to increase volume or weight, but can compromise the quality or safety of the original item. Substitutes are generally legal and acceptable, whereas adulterants are typically considered harmful or fraudulent.