A second is a unit of time.

There are sixty seconds in \(1\) minute and sixty minutes in one hour, so there are \(3,600\) seconds in one hour.

The clock in the picture has a third hand that shows the seconds. It is the thin hand that is just past the \(1\) in the picture. It is the hand that moves the fastest.

You can roughly count seconds by saying "one one-thousand, two one-thousand, three one-thousand, four one-thousand," etc.

The heart of a fit person who is resting usually beats at around \(60\) beats per minute. So, each beat of their heart takes approximately \(1 \text{ second}\).

Smaller units of time are sometimes needed, for example, when taking times in a swimming race or in computing. These include the millisecond (one-thousandth of a second), the microsecond (one-millionth of a second) and the nanosecond (one billionth of a second)