3 used for adding information or a comment about a particular thing or fact when it is already clear what that thing or fact is
Bogart starred in the film Casablanca, which was made in 1942.
A skilled workforce is essential, which is why our training programme is so important.
The search will not begin until dawn, by which time it will probably be too late.
in which case (=if this happens): Of course it may rain, in which case we shall have to hold the ceremony indoors.
Synonyms and related words