In the last lesson, we said that many common nouns can be singular (one) or plural (more than one). We talked about how to change a noun from singular to plural. For example:

Singular	Plural
book	books
cat	cats
teacher	teachers
house	houses
box	boxes
baby	babies
knife	knives

However, there are some nouns that are irregular. We do not add ‘-s' to make them plural. We need to change them in a different way. In this lesson, we will cover all of the irregular plural nouns that you need to know.

There is no special rule for these nouns. We must memorize them. It is very important to memorize these nouns because many of them are very common words.

Here is a list of all the irregular plural nouns.

Singular	Plural
man	men
woman	women
child	children
person	people
foot	feet
tooth	teeth
mouse	mice
goose	geese
cactus	cacti
syllabus	syllabi
diagnosis	diagnoses
oasis	oases
crisis	crises
fungus	fungi
nucleus	nuclei
analysis	analyses

Some of these words you must know such as men, women, child, people, and feet.Some of the other words you might not need to use a lot. So, start with the most common words and memorized them first. Later, depending on your job, university major, or interests you can learn other ones.

My guess is that even most native speakers do not know all of these. So, you do not need to stress or worry about learning them.

Nouns which are always plural

Some nouns are always used in plural form. This is because they are a set. There are two things working together as one. Here is a list.

• glasses (eyeglasses; not a glass for drinking or windows)
• sunglasses
• pants
• clothes
• scissors
• binoculars
• tweezers

Nouns that look plural, but are singular

Some look like they are plural, but are considered singular. These words end in ‘-s', but they are not plural.

• news
• billiards
• athletics
• linguistics

Here are some example sentences.

• The news is interesting to me.
• Billiards is hard.

Nouns that have the same plural and singular form

Some nouns are the same in both singular and plural form.

• sheep
• fish
• deer
• aircraft
• species

We can usually tell if the noun is singular or plural from other words or clues in the sentence. Here are some examples.

• I have one sheep, but my neighbor has 10 sheep.
• There is a red fish and 20 yellow fish.

Make sure that you understand this basic English grammar well. It can be annoying to memorize these irregular plural nouns, but you must do it if you want to speak English fluently.