The form thief is the singular noun; the plural form is thieves.
The form thief's is the singular possessive form.The plural form of the noun thief is thieves.The plural possessive form is thieves'.Example: The thieves' hideout was raided by the police.
Thieves is already plural. The singular is thief.
The word "thieves" is already plural. The singular is "thief."
The plural form of the noun thief is thieves.The plural possessive form is thieves' (just the apostrophe).Example: The thieves' car hit a stop sign and foiled their getaway.
Guilt is an uncountable noun for a state or feeling. It has no singular or plural.
The singular form of the plural noun thieves is thief.
The form thief's is the singular possessive form.The plural form of the noun thief is thieves.The plural possessive form is thieves'.Example: The thieves' hideout was raided by the police.
Thieves is already plural. The singular is thief.
The noun 'mice' is the plural form of the singular noun 'mouse'.
The singular noun is "louse" and the plural noun is "lice."
noun that are plural in form but singular in meaning
The noun children is the plural form of the singular noun child.
The noun 'circus' is a singular noun.The plural noun is 'circuses'.
The noun juggler is a singular noun. The plural noun is jugglers.
The singular noun is trio; the plural noun is trios.
The singular noun is Tuesday.The plural noun is Tuesdays.
The noun 'orchid' is a singular noun, a word for one.The plural noun is 'orchids'.