au fait
adjective /ˌəʊ ˈfeɪ/
  /ˌəʊ ˈfeɪ/
[not before noun] (from French)- au fait (with something) completely familiar with something完全熟悉 - I'm new here so I'm not completely au fait with the system.我初来乍到,所以对这个系统还不完全熟悉。 
 词源mid 18th cent.: from French, literally ‘to the fact, to the point’.
- I'm new here so I'm not completely au fait with the system.