Is it plural or not? Analyze the questions and answers to remember the rule.

Which one is correct? Hint: Adjectives in English remain unchanged regardless of number—they don't take plural endings.

Retirement plans vary depending on whether employees are 60 years old or younger.

Retirement plans vary depending on whether employees are 60-years-olds or younger.

He makes $60,000 per year. How is the number in that sentence pronounced?

The consultant charged a three-thousand-dollar fee for the business analysis.

The consultant charged a three-thousand-dollars fee for the business analysis.

The consultant charged three thousand dollars for the consultation.

The consultant charged three-thousand-dollar for the consultation.

Many thirty-years-old professionals are switching careers for better work-life balance.

Many thirty-year-old professionals are switching careers for better work-life balance.