While the adjectives substantial and substantive slighly differ in their meaning in everyday English, they have completely different meanings in legal context.
Substantive generally means real, meaningful, and it refers to something that exists. In legal context, reference is often made to substantive law, which is the part of the law that describes the rights and obligations, rather than the means of enforcing the rights and obligations, which is referred to as procedural law.
Substantial is more about a big thing,
