spelling: plurals of foreign nouns

Many nouns that have come into English from other languages continue to form their plurals according to the rules for pluralization in the source language. However, some have an English plural form in addition to, or instead of, the foreign form. In some cases, the different plural forms have different meanings or uses.

Note the following singular and plural forms.

Nouns ending in -a

• alumna: alumnae
• antenna: antennae (feelers) or antennas (aerials)
• formula: formulas or formulae

Nouns ending in -eau

• bureau: bureaus (British: bureaux)
• plateau: plateaus or plateaux

Nouns ending in -ex or -ix

• appendix: appendixes or appendices
• index: indexes (of a book) or indices (in mathematics, statistics)
• matrix: matrices

Nouns ending in -is

• analysis: analyses
• basis: bases
• crisis: crises
• ellipsis: ellipses
• hypothesis: hypotheses
• parenthesis: parentheses

Nouns ending in -on

• criterion: criteria
• phenomenon: phenomena

Nouns ending in -um

• addendum: addenda
• bacterium: bacteria
• erratum: errata
• medium: mediums or media (check dictionary for plural form to use in a given context)
• memorandum: memorandums or memoranda
• symposium: symposiums or symposia

Nouns ending in -us

• alumnus: alumni
• bus: buses
• census: censuses
• focus: focuses or foci (not focusses, which is a verb form)
• nucleus: nuclei
• surplus: surpluses

© Public Services and Procurement Canada, 2025
TERMIUM Plus^®, the Government of Canada's terminology and linguistic data bank
Writing tools – Writing Tips
A product of the Translation Bureau