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.
J. Carmichael. By shutting off a single gene, researchers think humans could regenerate damaged tissue just as newts do. Scientists have long been stymied by human regenerative healing -- that is, wholesale regrowth of, say, a severed limb -- an ability inherent in some species but lost on humans.