The possessive noun chef's is singular, referring to something belonging to one chef.
The plural noun is chefs.
The plural possessive noun is chefs'.
Examples:
The chef's hat fell into the soup pot. (singular, the hat of one chef)
Both chefs' utensils are kept in separate locked cabinets. (plural, the utensils of two chefs)
The singular possessive form of "test" is "test's".
The singular possessive pronouns are mine, yours, his, hers, and its. The singular possessive adjectives are my, your, his, her, and its.
The singular possessive is ant's.The plural possessive is ants'.
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive of dish is dish's
Taco's is the singular possessive.
The singular possessive form is classmate's.
The singular possessive is biker's; the plural possessive is bikers'.
The singular possessive is fish's.
Grave's is the singular possessive.
The singular possessive is Martin's.
Buzz's is the singular possessive.