octopi

Created in Latin by analogy with pōlypus (“octopus”), which was either second or third declension in both Latin and Greek, though historically third in the latter.

octopi

1. (nonstandard) plural of octopus

   Synonyms: octopuses, octopodes (see more in main entry)

   • 2009, Keith Spicer, Paris Passions: Watching the French Being Brilliant and Bizarre, BookSurge, →ISBN, page 43:

     Cuddling is what an epidemic of lovers are doing all around us on this nippy, dazzling day. Entangled in each other like doting octopi, sweethearts are seizing the day, the hour, the magic minute.

The forms octopuses and octopi appear roughly equally prevalent, with octopodes being much rarer. However, octopi is nonstandard in US English. See octopus for further discussion.