讓我們開門見山，表達幾歲一般用以下幾種說法。
如：奧黛麗·赫本那時19歲。
Audrey Hepburn was 19.
Audrey Hepburn was 19 years old.
Audrey Hepburn was a 19-year-old.
Audrey Hepburn was a 19-year-old girl.
從這個例子可以看出，
1，表示多少歲，可以直接用數字：
My elder brother is 25.
我哥哥二十五歲。
2，表示多少歲，可以直接用數字+years+old：
Jane’s mother was 26 years old when she married Jane’s father.
簡的母親嫁給簡的父親時才26歲。
3，表示歲數的時候加連字符「-」，可以做形容詞修飾名詞或直接代替名詞：
The 16-year-old boy was admitted in the university.
這個16歲的男孩被大學錄取了。
This is a birthday party for 10-year-olds.
這是一個10歲的孩子們開的生日聚會。
注意，加連字符「-」，year不能用複數years
That bottle of Maotai is 25 years old.
That bottle of Maotai is 25-year-old.
那瓶茅臺酒已經25年了。
另外還有一個小問題，表示幾歲的數字要不要拼寫出來？
She is 19 years old.還是She is nineteen years old？
國外的權威寫作指南都傾向於直接用數字，不拼寫。
但簡單的數字人們也常常拼寫出來
My baby just turned 2/two years old.
可以理解的是，用數字表達更簡明易懂：
We are celebrating the 150-year anniversary of our university.
We are celebrating the one hundred and fifty year anniversary of our university.
我們正在慶祝我們大學150周年校慶。
（沒人會寫成第二句裡的拼寫）
如果想說一個人二十幾歲，或五十幾歲，用in his or her 20s/50s表達：
People who are in their 40s and 50s will like it.
四五十歲的人會喜歡的。
Victims of mugging are typically young women in their early 20s.
搶劫案的受害者通常是20出頭的年輕女性。
Most athletes reach their peak in their mid 20s.
大多數運動員在 25 歲左右達到巔峰狀態。
He was in his late 20s.
他年近三十。
表示一個人比另一個人年輕/年長几歲，不要只會...younger/older than，請看以前的介紹：
「年輕幾歲」只會說……years younger? 那你就out了！
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