What is the term for the age of a rock given as the number of years since the rock formed?

The term that refers to the age of a rock given as the number of years since the rock formed is absolute age. This concept is essential in geology because it allows scientists to determine the specific time frame in which geological events occurred. Absolute age is typically established through radiometric dating techniques, which measure the decay of radioactive isotopes within rocks. By quantifying the age in years, scientists can construct a timeline of Earth's history and better understand the processes that have shaped our planet.

Relative age, in contrast, describes the order of events or the age of rocks in relation to one another but does not provide specific numerical values. Geochronology is the broader field that studies the age of Earth materials and the timing of events in Earth's history, encompassing various dating methods. Numerical age, while similar to absolute age, is not the commonly used term in the context of geology. Thus, absolute age is the correct answer, emphasizing the significance of knowing the exact age of geological materials.