when is the union jack called the union jack
Union Jack The terms Union Jack and Union Flag are both historically correct for describing the de facto national flag of the United Kingdom. Whether the term Union Jack applies only when used as a jack flag on a ship is a modern matter of debate.[9]
Union station A union station (also known as a union terminal and a joint station in Europe) is a railway station where tracks and facilities are shared by two or more separate railway companies, allowing passengers to connect conveniently between them. The term 'union station' is used in North America and 'joint station' is used in Europe.