How many pieces of human abdominal muscles are there?

People often say that "abdominal muscle" generally refers to "rectus abdominis", with only two pieces, which are distributed in pairs on both sides of the midline of the anterior abdominal wall. Each rectus abdominis muscle can have 3-4 abdominal muscles, that is, the parts where the muscles can contract and bulge. How many abdominal muscles each person has is determined by nature, and one or more will not grow because of exercise. It can only be manifested because exercise makes muscle fibers developed or because muscle fibers are weak.