thousandth

Imagine dividing something into one thousand equal pieces. One piece would be just one out of a thousand. We use "thousandth" for that very small fraction and also for the number or thing in position 1000 in a series. For example, rounding a number to the nearest thousandth means keeping three decimal places. A race might be decided by a thousandth of a second, which is a very tiny difference.

The word "thousandth" can be used in two main ways. First, it is an ordinal number, so it can tell us the position of something in a sequence: the thousandth person in line, the thousandth page, or the thousandth visit. Second, it can mean one part out of one thousand. If you write 0.001, that is one thousandth. In 10.003, the "3" is in the thousandths place, so it means three-thousandths.

You will often see this word in math, science, engineering, and timing, where small differences matter. A machine part might be measured to the nearest thousandth of an inch. A race might be won by a thousandth of a second. In decimal numbers, the thousandth place is the third digit to the right of the decimal point.

So this word is useful both for order and for amount. It can name the item in position 1000, or it can describe a very small fraction: one part in a thousand. When you meet it in real life, it usually points to careful counting, exact measurement, or very fine detail.