Why is 240V electric called “single phase” despite being two 120V hots 180° out of phase?

Question

One hot conductor and a neutral is called single phase; that makes complete sense. It continues to make sense with three phase power where you have three separate hot conductors. Why does the logic fall apart when you have two hot conductors? And if there is a reason why those two hot conductors are called single phase, why is the first example of a single hot and a neutral also called single phase?

In: 1

Answer 1

In the UK the 3 phase supply is transformed down to 415V per phase on the secondary side of the transformer. The secondary windings are in a star configuration and the star point is used for a neutral conductor. The measurement between any one phase and neutral is 220V and is hence known as a single phase.