common currency

1. Literally, a form of money that is used in multiple countries. Euros are a common currency, so you can use them both when you're in Ireland and afterward when you go to Italy. I only have dollars, so I'm afraid to ask what the common currency is here. Is the dinar still the common currency in the Middle East?

2. By extension, something that is prevalent in use or acceptance. The economic approach is now common currency as it is being used by the majority of developed countries. Back before germ theory became common currency, it was widely believed that poisonous air caused illnesses. It is a term that became common currency in the wake of the disaster, spreading on social media like wildfire.