Grammar tips

Today we will take a look at irregular plural nouns, which are nouns that do not become plural by adding -s or -es, as most nouns in the English language do. Particularly, we will dive into plurals of Latin and Greek words, which are commonly used in mathematical and scientific contexts.

Nouns ending in -us

To make a word ending in -us plural, change -us to -i.

• Examples: fungus (fungi); nucleus (nuclei); cactus (cacti); alumnus (alumni).

Irregular formation of nouns ending in -is

Nouns with an -is ending can be made plural by changing -is to -es.

• Examples: axis (axes); analysis (analyses); crisis (crises); thesis (theses).

Irregular formation of nouns ending in -on

These Greek words change their -on ending to -a.

• Examples: phenomenon (phenomena); criterion (criteria).

Irregular formation of nouns ending in -um

Words ending in -um lose their -um and replace it with -a to form a plural.

• Examples: datum (data); memorandum (memoranda); bacterium (bacteria); stratum (strata); curriculum (curricula - also curriculums).

*Note: In a similar sense, the term millennium also changes to an a in the plural form - millennia.

These irregular noun forms are common questions asked in the 1st phase of the CACD examination, so BEWARE!

In the near future, we'll take a look at some other irregular noun forms as well. Stay tuned!