PrintWhat 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.