Apt and Au fait

Apt adjective - Having a tendency to be or act in a certain way.

Au fait and apt are semantically related. In some cases you can use "Au fait" instead an adjective "Apt".

Au fait adjective - Being up to particular standard or level especially in being up to date in knowledge.

Apt and au fait are semantically related. Sometimes you can use "Apt" instead an adjective phrase "Au fait".