noun
average age; mean age
Used in statistical, demographic, or general contexts to refer to the arithmetic mean of ages in a group.
このクラスの平均年齢は20歳です。
The average age of this class is 20.
日本の平均年齢は年々上がっている。
Japan's average age is rising year by year.
Compound of 平均 (average) + 年齢 (age).