Unit 3.1

Irregular Plural Nouns: Borrowings


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Nouns refer to a person, place, thing, event or substance.

Borrowings or loanwords are some words whose origins come from other languages (source languages). So, some nouns don’t follow the rules, they’re irregular and their plural is formed differently.


Usually borrowings have an irregular plural form.

The most commonly used are:

Cactus Cacti / cactuses
Datum Data
Fungus Fungi
Index Indices
Medium Media
Oasis Oases
Thesis Theses


Cactus ⇒There are so many cacti in their garden!

Datum ⇒ I lost my SD memory card and all my data.

Fungus⇒ There are many types of edible fungi.

Index ⇒ The law of rational indices seems to be very complicated.

Medium ⇒ There are more and more disadvantages of media nowadays.

Oasis ⇒ Oases are home to many animals.

Thesis ⇒ We had to read the 95 theses by Martin Luther King.


We use borrowed nouns as normal nouns.

We just have to remember that their plurals are irregular.


Borrowings or loanwords are words whose origins are from other languages. Usually borrowings have an irregular plural form.

The most commonly used are: cactus ⇒ cactidatum ⇒ data, fungus ⇒ fungi, index ⇒ indices, medium ⇒ media, oasis ⇒ oases, thesis ⇒ theses

For example:
” A fungus.” ⇒  “Three fungi.” / “Three funguses.”
“There is only one cactus in my balcony.” ⇒ “There are six cacti in my balcony.”

Let’s revise this content within the {Form} section. Take a look at the {Example} section that shows its use within a context.

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