Effective Technical Writing in the Information Age

Tricky Singular Plural Pairs


What follows are some important and commonly misused singular/plural pairs, all of which are commonly used in technical writing.

Singular Plural
alga algae
appendix appendixes or appendices
axis axes
crisis crises
criterion criteria
curriculum curriculums or curricula
formula formulas or formulae
fungus fungi
hypothesis hypotheses
locus loci
medium media
nucleus nuclei
phenomenon phenomena
radius radii
retina retinas or retinae
spectrum spectra
stimulus stimuli
stratum strata
thesis theses

Be certain to use the correct form of these nouns, and be sure that the related verbs are compatible with the noun’s status as singular or plural. Even though they may automatically sound wrong to your ear, the sentences below are all correct, with the subjects and verbs compatible in grammar.

The emission spectra of the bodies peak in the infrared.

The media are highly influential in shaping public opinion.

A stratum of sand was struck as they dug the well.

The radii of error spheres are more difficult to determine than the centers.