penumbra
noun /pəˈnʌmbrə/
/pəˈnʌmbrə/
(specialist)- an area of shadow which is between fully dark and fully light
（黑暗与光明之间的）半影 - (astronomy
天文学 （偏食期间的）半影
词源mid 17th cent.: modern Latin, from Latin paene ‘almost’ + umbra ‘shadow’.