What is the basic unit for measuring time?

The second is recognized as the basic unit for measuring time in the International System of Units (SI). It serves as the foundation for defining larger units of time, such as minutes, hours, and days. The definition of a second is based on atomic timekeeping, specifically related to the vibrations of cesium atoms, making it the most precise and scientifically accepted measure of time.

While minutes and hours are derived from the second—there are 60 seconds in a minute and 3600 seconds in an hour—these units are not considered fundamental. The day is also a larger unit based on the Earth's rotation but is still categorized as a composite of seconds. Therefore, the correct answer emphasizes the second's role as the fundamental measurement from which all other units of time are derived.