Sentence:  Two of Saturn's small moons have the unique distinction of sharing the same orbit. Epimetheus and <WSD>Janus</WSD> circle the Lord of the Rings at a distance of just over 151,000 km, about half the distance from Earth to the Moon. Both are irregularly shaped. <WSD>Janus</WSD> is 179 km across, while Epimetheus is about 116 km in diameter. 
Meaning of the word marked with <WSD> tags:  A moon of Saturn.