nocturnal       
adjective  formal uk/nɒkˈtɜː.nəl/ us/nɑːkˈtɝː.nəl/
 夜间发生的;夜间活动的;夜间的
happening in or active during the night, or relating to the night
  nocturnal wanderings 夜游 
 nocturnal light 夜光 
 Most bats are nocturnal. 大部分蝙蝠在夜间活动。 
 Compare: diurnal