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 |