Collins Cobuild English Grammar (187 page)

BOOK: Collins Cobuild English Grammar
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R18
    With some nouns ending in
a
, the plurals are formed by adding
e
.
larva
larvae
vertebra
vertebrae

Some, such as
antenna
,
formula
,
amoeba
, and
nebula
, also have less formal plurals ending in
s
.

R19
    Other nouns form their plurals in other ways. Some of these have two plural forms, one formed with
s
and one formed in a different way. Usually the form with
s
is used in less formal English.
appendix
appendices
or
appendixes
automaton
automata
or
automatons
corpus
corpora
or
corpuses
criterion
criteria
genus
genera
index
indices
or
indexes
matrix
matrices
phenomenon
phenomena
tempo
tempi
or
tempos
virtuoso
virtuosi
or
virtuosos
vortex
vortices

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