The Plural Of Octopus — Is It Octopi Or Octopuses?

English can be confusing, especially to non-native speakers. We speak words gathered from many sources that are usually in English rather than the native form. It is not as easy as adding -s or -es. So, in this article, we will dive deep into the plural of octopus.

Occasionally, words are written and have a finalized form in English, particularly those with Latin origins. Other times, words retain the plural forms of their original language. This article aims to shed light on the correct plural of octopus while examining its etymological roots. We will also discuss the new Latin plural system and some facts about octopi.

What is an octopus?

giant pacific octopus
A giant Pacific octopus. Photo: iStock.

An octopus is a solitary creature that resides on various levels in the ocean. The different types of octopus are a member of the class Cephalopoda, which means head foot in Greek. It simply refers to the tentacles attached to an octopus' head. They use these eight long arms to walk across the ocean floor. 

Because of the suction cups on each underside, these tentacles are sensitive to touch and taste. An octopus also has a hard beak used to crush the shells of crustacean prey. This unique marine species has three hearts: two hearts pump blood to the gills, while the third heart pumps blood through the rest of the body.  

What is the correct plural of octopus? 

In the English language, there is more than one plural form of octopus. The three plurals of octopus are octopi, octopuses, and octopodes. However, let us examine the etymology of octopus before discussing how to pluralize octopus. 

Etymology of Octopus  

The earliest use of the word octopus was in 1759. The word octopus is of Latin origin derived from the Greek word októpus. Októpus means 'eight-foot' and refers to the octopus's eight tentacles. 

From its etymology, you can tell the reasons for varying plurals. It goes back to three different languages with different rules for pluralizing words. In the following sections, we will examine the plural form of octopus in Greek, Latin, and English.

Greek Ending: Octopodes  

Octopus was originally Greek (októpus), so it has a Greek plural form like other Greek words. According to the Merriam-Webster Dictionary, the plural of octopus is octopodes. However, despite its Greek origin, the word is rarely used in English.

Latin Ending: Octopi 

Octopi is the oldest of the three plural forms of octopus. Octopus is a Latin word, and words of Latin origin should have Latin endings. Hence, the Latinized form, octopi. Most plural Latin endings require the single addition of the letter -i in English.

English Ending: Octopuses  

The English word has its plural form outside of New Latin. Adding the -es ending changes it to octopuses, the most used plural endings.

Octopi Debate: Considering the prescriptive and descriptive grammar approach.

blue ringed octopus
Photo by Angell Williams on Flickr licensed under CC BY 2.0 (Cropped from original)

A prescriptive grammar approach refers to the specific rules of how a language must be used. These rules dictate how you write and speak a language, with its primary focus on grammar and syntactic constructions. Deviating from these rules means you speak incorrect English.

Descriptive grammar focuses on describing language as it is used instead of dictating how it should be spoken. It regards language from the standpoint of how speakers use it in their daily lives. 

According to these perspectives, there are two correct ways to refer to more than one octopus: octopuses and octopi. A prescriptive approach would prefer octopuses because they follow the English grammatical structure.

Meanwhile, a descriptive's preferred plural is Octopi. This recognizes the Greek pous (foot) and the Latin origin of Octopus in English, adhering to the Latinized form.

Types of Latin Noun Plurals

A Latin noun ending refers to the change at the end letters of a word to make it plural1. There are five declension groups, a pattern that shows gender, quantity, and grammatical case. 

The first declension ending changes singular words that end with: 

  • Nominative case -a to -ae
  • Genitive case ae to ãrum 
  • Dative case ae to īs
  • Accusative case am to às
  • Ablative case ã to īs

Second declension endings change single words that end with: 

  • Nominative case us/er to ī
  • Genitive case ī to ōrum
  • Dative case ō to īs
  • Accusative case um to ōs
  • Ablative case ō to īs

Third declension endings change masculine and feminine words that end with: 

  • Genitive case is to um
  • Dative case ī to ibus
  • Accusative case em to ēs
  • Ablative case e to ibus 

Fourth declension noun endings switch singular masculine words that end with: 

  • Nominative case us to ūs
  • Genitive case ūs to uum
  • Dative case to ibus
  • Accusative case um to ūs
  • Ablative case ū to ibus

Fifth declension endings change feminine words that end with: 

  • Nominative case ēs to ēs
  • Genitive case eī / ēī to ērum
  • Dative case eī / ēī to ēbus
  • Accusative case em to ēs
  • Ablative case ē to ēbus

Octopi Plural Illustrations

dumbo octopus grimpoteuthis
Photo by NOAA Ocean Exploration & Research on Wikimedia Commons licensed under CC BY-SA 2.0 (Cropped from original).

This section will explore some facts about octopuses while using various plural forms.

Octopi has more than one brain.

Octopi are a unique species with nine working brains. The central brain, located between their eyes, is responsible for the octopus's incredible memory, transmitting nervous impulses and interpreting sensory information. Eight tiny brains rest under the base of the octopus's tentacles.

Octopuses have three hearts.

Octopuses have three hearts to keep them alive. Two hearts move blood to their gills, while the third heart keeps pumping blood to the organs.

Their defense system is a harmful ink.

Octopuses produce ink containing a compound known as tyrosinase. This compound is in humans and helps us control natural melanin production. However, the ink causes a blinding irritation when it touches predators' eyes. It's so potent that octopuses that do not escape their ink die.

Read more: Octopus facts.

Conclusion: Plural Of Octopus

The amalgamation of various languages makes some English words sound peculiar, making it difficult to recognize the correct plural for words like octopus. Considering the word’s history, it is safe to say that all three plurals are technically correct. However, we only use octopi and octopuses in various places in the world.

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Smith, P. (2016). Greek and Latin Roots: Part I - Latin. Pressbooks.

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