The singular form of the word "criteria" is "criterion."
The word 'duo' is the singular form; the plural form is duos.
No. Apostrophes are almost never used to form a plural.The spelling ski's is a possessive noun, e.g.He has to be careful of his left ski's position on the last turn.His right ski's color is black and his left ski's color is white.
The singular form of the word flagella is flagellum.
The plural form for the noun ski, or any noun ending with -ski, is skis (-skis).
The singular form of the word "señores" is "señor."
That is the singular form; the plural form is those.
'Jackhammer' is the singular form.
The singular form is commando.
The singular possessive form of the word "jury" is "jury's."
The word dog is the singular form.
"Biopsy" is the singular form, while "biopsies" is the plural form.