Gasses vs. Gases – Which Is the Correct Plural?
Gases is the usual plural. Gasses is the simple-present verb.
Media vs. Mediums – What’s the Difference?
Both plurals are commonly used, though each tends to appear more often in certain uses.
Spectra vs. spectrums
The Latin form, spectra prevails, but the English plural is not incorrect and is slowly gaining ground.
Biceps and triceps
Biceps and triceps are technically singular nouns, but they’re informally treated as plural, with bicep and tricep being the informal singular forms.
Treasurys
In reference to U.S. Treasury bonds, treasury is pluralized in an unconventional way: Treasurys.
Dwarfs vs. dwarves
Dwarves in fantasy fiction; dwarfs everywhere else.
Scissors
It is usually treated as plural, but making it singular is not wrong.