Erstwhile and Ex

Erstwhile adjective - Having been such at some previous time.

Ex and erstwhile are semantically related in former topic. In some cases you can use "Ex" instead an adjective "Erstwhile".

Ex adjective - Out of fashion.

Erstwhile and ex are semantically related in dead topic. You can use "Erstwhile" instead an adjective "Ex", if it concerns topics such as former, olden, previous in time or order.