syzygy

In a sentence.

1. 01

   A solar eclipse requires a syzygy of the Sun, Moon, and Earth.

2. 02

   The diagram showed the syzygy that occurs at a full moon.

Where it came from.

Syzygy came through Late Latin from Greek syzygia, meaning ‘union,’ ‘pair,’ or ‘yoke.’ Astronomy gave that joining a precise geometric sense.

Why it’s interesting.

A word with three y's describes three bodies lined up in space.