Age

The age of something/someone is how old he/she/it is. Normally it is the number of years he/she/it has existed. Often we talk about the age of persons: "he is five years of age"; "she is twenty years old." However, age can be used for just about anything. For example, a rock's age may be 3 million years since formation, or even our planet, Earth, can be said to have an age of 4.54 billion years.

Another use of the word age is to assign it to a time period. For example, the period in a culture when the most advanced metalworking is done using the metal bronze, we call that culture's bronze age. To illustrate, the Bronze Age in Europe is the period from 2300-600 BC, while the same period for China is 2000-700 BC. Sometimes the period is not so clearly defined, such as the "age of the dinosaurs"—the period when dinosaurs roamed the earth.