chin seems to be translated as both 下巴 and 頷. Is there absolutely no difference? Is one more common than the other? I find it strange that there are two translations for so many words in Chinese, especially for specific words like chin that have little ambiguity.
When I look up pictures for the word 頷, I see more medical pictures, for 下巴, more regular pictures. Is 頷 something more concrete than chin? My dictionary says just "chin".