Lingua franca = a language used for day-to-day public communication, which is not the speakers’ own language.
- English is a lingua franca in a lot of countries nowadays.
- English is the lingua franca of the literate in India.
Jog someone’s memory = cause someone to remember something suddenly.
- I tried jogging mom’s memory , but she couldn’t remember Joe’s phone number either.
- I tried to jog Bill’s memory about our childhood antics.
- Maybe this photograph will jog your memory.
In/within living memory = within or during the time that is remembered by people still alive.
- The worst recession in living memory.
- There hasn’t been a blizzard like this in living memory.
- These are the worst floods in Kerala within living memory.