In science, we use the International System of Units (SI) to keep measurements the same around the world. The SI unit for time is called a second. It is the most basic and widely used unit to measure how long something takes.

Everything from a quick blink to the rotation of Earth is measured in seconds. One second is defined very accurately using atomic clocks, which are used in science and technology to keep perfect time.

Other units of time like minutes, hours, and days are based on seconds. For example, one minute has 60 seconds, and one hour has 3,600 seconds. This makes seconds the building block for all other time measurements.

The other options — kilogram, meter, and volt — are SI units too, but for different things. Kilogram is used to measure mass, meter is for length, and volt is for electric potential.

So, the next time someone asks you what the SI unit of time is, you can confidently say it’s the second. It’s a small word with big importance in science and everyday life.