Definition of opacity for English Language Learners. : 1  the quality of a material that does not allow light to pass through it : the quality of being opaque. : 2  the quality of being difficult to understand or explain.
Research has shown that this is not true, and that brain cells can and do regenerate, especially in the areas related to learning, decision-making, visual recognition, and the way people perceive objects in space.weet. For a long time, scientists thought that it was impossible for brain cells to regenerate because they assumed that any new cells would disrupt the order of the brain.
1 Any cerebral cortex neurons that die are not replaced. 2  Fat cells are replaced at the rate of about 10% per year in adults. 3  So you could say that on average, human beings replace all their fat cells about every ten years. 4  Cardiomyocyte heart cells are replaced at a reducing rate as we age.