Read Collins Cobuild English Grammar Online
Authors: Collins
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 |