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.
History of human tissue regeneration. In humans with non-injured tissues, the tissue is naturally regenerated over time; by default these tissues have new cells available to replace expended cells. For example, the body regenerates a full bone within 10 years, while non-injured skin tissue is regenerated within two weeks.