Singular or plural nouns 

Irregular Nouns That End in -Us

Some irregular nouns end in -us, like alumnus and
cactus. To make these words plural, drop the -us and add an
-i. For instance, “Many colleges request donations from
alumni.” There are, of course, exceptions to this rule. For instance, the aforementioned alumni attended different college
campuses, not college campi.

Singular or plural nouns

Irregular Nouns That Don’t Change

Not all nouns follow the same rules. Some are exactly the same in their singular and plural forms. The word
sheep, for instance, can mean one woolly animal or many woolly animals. The word
can mean one airplane or many airplanes.

At the same time, some irregular nouns only exist in their plural form. For example, there’s no singular form of
scissors, pants, species, or shorts.

Singular or plural nouns 

Irregular Nouns That End in -Y

Some irregular nouns that end in -y are made plural by changing the
y to an i and adding -es. For instance,
baby becomes babies, and lady becomes ladies. But, if it ends in a vowel followed by
y, it’s actually a regular noun. For example, “Santa brings
toys to children by climbing down their

Confused Plural in Countable Nouns

A. Some words, however, remain the same for plural.

  • deer – deer
  • sheep – sheep
  • salmon – salmon
  • mackerel – mackerel

B. An “a” ending

  • phenomenon – phenomena
  • criterion – criteria

C. A change from um to a

  • curriculum – curricula
  • medium – media
  • memorandum – memoranda

D. A change of end letters to es or i for foreign words that have become part of English.

  • Virus – viruses
  • octopus – octopuses
  • circus – circuses
  • stimulus – stimuli
  • syllabus – syllabuses or syllabi
  • terminus – terminuses or termini