Black lips or having very dark colored lips is contributed by several factors and can be used as indicators for certain conditions that are happening inside the body. Though very rare, there are certain severe medical conditions that can cause the lips to turn a darker shade or even black like having cancer. It can be contributed by living a modern lifestyle, certain eating habits, and some medications. There are patients that naturally have black lips or dark-colored lips.
Substantial - either now or in the next three months. 1  significant harm or danger due to your physical or mental health or behaviour.  being unable to carry out many personal care and daily household chores, causing significant risks to your independence.
Substantial vs. substantive Something that is substantial is (1) of considerable size or importance, (2) solidly built, (3) ample, or (4) well-to-do. Substantive means of or relating to substance, where substance means meaning. So substantive is often synonymous with meaningful, while substantial is usually synonymous with large or important. 1 To 1 English native Teachers, the best way to improve your English!