79. Letters of the alphabet, figures, signs used in writing, and words regarded merely as words take ’s in the plural.

80. Foreign nouns in English sometimes retain their foreign plurals; but many have an English plural also.

Some of the commonest are included in the following list:[12]

SingularPlural
alumna (feminine)alumnæ
alumnus (masculine)alumni
amanuensisamanuenses
analysisanalyses
animalculumanimalcula[13]
antithesisantitheses
appendixappendices
appendixes
axisaxes
bacillusbacilli
bacteriumbacteria
banditbanditti
bandits
basisbases
beaubeaux
beaus
candelabrumcandelabra
cumuluscumuli
cherubcherubim
cherubs
crisiscrises
curriculumcurricula
datumdata
ellipsisellipses
erratumerrata
formulaformulæ
formulas
geniusgenii
geniuses
genusgenera
gymnasiumgymnasia
gymnasiums
hippopotamushippopotami
hypothesishypotheses
larvalarvæ
memorandummemoranda
memorandums
nebulanebulæ
oasisoases
parenthesisparentheses
phenomenonphenomena
radiusradii
seraphseraphim
seraphs
speciesspecies
stratumstrata
synopsissynopses
tableautableaux
tempotempi
terminustermini
thesistheses
trousseautrousseaux
vertebravertebræ

The two plurals sometimes differ in meaning: as,—

81. When a proper name with the title Mr., Mrs., Miss, or Master, is put into the plural, the rules are as follows:—

1. The plural of Mr. is Messrs. (pronounced Messers[14]). The name remains in the singular. Thus,—