Here’s a secret weapon word for serious Scrabble competitors: syzygy. The shortest word to incorporate three y’s, it’s also a term shared by poetry and astronomy. For poets, the phenomenon takes two forms: phonetic syzygy (similar to alliteration but including sounds within words), and metrical syzygy (the repetition of rhythms in the meter of the poem). For astronomers, syzygy is shorthand for the straight-line alignment of celestial bodies in the same system—a line-up of Jupiter and Mars, for example. But to understand why poetry and astronomy share this weird word, we need to look at its etymological root. It enters English via Latin (suzugia) from the Greek syzygos, meaning yoked or paired. From there, it was broadly applied to describe linked things in literature, astronomy, and other fields. Lest you think that applications of the term are rare and unrelated across these fields, you’re witnessing an example every time you look up at the full moon. And what could be more poetic than that?