General Rules
* Use numerals for ages 10 and above. For example: "The 12-year-old boy..." or "The 35-year-old woman..."
* Use words for ages under 10. For example: "The two-year-old child..." or "The nine-year-old girl..."
* Avoid using hyphens between the age and the word "year" if the word "year" is plural. For example: "The 50-year-old woman..." or "The children are 8 years old."
* Place the age after the noun it modifies. For example: "The woman, 50,..." or "The boy, 12,..."
Specific Situations
* In a table or figure: You can use numerals for all ages, even under 10.
* In a research paper: Use numerals for all ages if it is important to emphasize the precise age. However, if the age is not a critical factor, you can use words for ages under 10.
* When referring to a person's age range: You can use numerals for both the lower and upper limits. For example: "The participants were between 18 and 25 years old."
Examples
* "The 10-year-old girl was playing in the park."
* "The 35-year-old man had been working for the company for 10 years."
* "The children were 5 years old."
* "The participants were between 20 and 30 years old."
Important Note: Always be mindful of the context and choose the style that best fits your purpose and audience.