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Plurals of Foreign Nouns

These nouns have irregular plural forms. They often make their plurals according to the rules of the language they were taken from (e.g. Latin or Greek) and an English plural spelling. Always use a good dictionary when using foreign plurals. Here are some examples.

1. Words of Latin origin

Singular Latin plural English plural
antenna antennae antennas
appendix appendices appendixes
cactus cacti cactuses
curriculum curricula curriculums
formula formulae formulas
index indices indexes
millennium millennia millenniums
referendum referenda referendums
stadium stadia stadiums
terminus termini analyses
thesaurus thesauri thesauruses
vortex vortices vortexes

2. Words of Greek origin

Nouns which end in -is usually come from Greek. Their plurals are made by changing the -is to -es:

Singular Plural
analysis analyses
axis axes
basis bases
crisis crises
diagnosis diagnoses
neurosis neuroses
thesis theses