Etymology and pluralisation
The
scientific Latin term
octopus was derived from
Ancient Greek ὀκτώπους, a
compound form of
ὀκτώ (
oktō, "eight") and
πούς (
pous, "foot"), itself a variant form of
ὀκτάπους, a word used for example by
Alexander of Tralles (c. 525–605) for the common octopus.
[4][5][6] The standard
pluralised form of "octopus" in English is "octopuses";
[7] the Ancient Greek plural ὀκτώποδες, "octopodes" (
/ɒkˈtɒpədiːz/), has also been used historically.
[8] The alternative plural "octopi" is considered grammatically incorrect because it
wrongly assumes that
octopus is a
Latin second declension "
-us" noun or adjective when, in either Greek or Latin, it is a
third declension noun.
[9][10] Fowler's Modern English Usage states that the only acceptable plural in English is "octopuses", that "octopi" is misconceived, and "octopodes"
pedantic;
[11][12][13] the latter is nonetheless used frequently enough to be acknowledged by the
descriptivist Merriam-Webster 11th Collegiate Dictionary and
Webster's New World College Dictionary. The
Oxford English Dictionary lists "octopuses", "octopi", and "octopodes", in that order, reflecting frequency of use, calling "octopodes" rare and noting that "octopi" is based on a misunderstanding.
[14] The
New Oxford American Dictionary (3rd Edition, 2010) lists "octopuses" as the only acceptable pluralisation, and indicates that "octopodes" is still occasionally used, but that "octopi" is incorrect.
[15]