ap ‧ er ‧ ture /ˈæpətʃə $ ˈæpərtʃʊr/ BrE AmE noun [countable]
[ Date: 1600-1700 ; Language: Latin ; Origin: apertura , from aperire 'to open' ]
1 . formal a small hole or space in something
2 . the small hole at the front of a camera, which can be made larger or smaller to let more or less light in when you take a photograph