1. (Physiology) the faculty or sense by which sound is perceived. 2. an opportunity to be listened to. 3. (General Physics) the range within which sound can be heard; earshot. 4. (Law) the investigation of a matter by a court of law, esp the preliminary inquiry into an indictable crime by magistrates. 5.
The grey hair ârule of thumbâ is that by the age of 50, half of the population have lost the colour in 50% of their hair. When researchers tested this rule, they found that 74% of people aged between 45 and 65 had grey hair, with an average intensity of 27%. Generally, men have more grey hair than women.
Why does hair turn gray? It is well known that gray hair results from a reduction of pigment, while white hair has no pigment, but why this happens remains somewhat of a mystery. Parents often cite having teenagers as the cause of gray hair. This is a good hypothesis, but scientists continue to investigate why hair turns gray. In time, everyoneâs hair turns gray. Your chance of going gray increases 10-20% every decade after 30 years. Initially, hair is white.