thousandth

Thousandth is a numerical term with several related meanings. As a fraction, it denotes one part in a thousand, namely 1/1000, whose decimal representation is 0.001. As an ordinal, thousandth designates the position of the item number 1000 in a sequence, the 1,000th element.

In decimal notation, the thousandth place is the third digit to the right of the decimal point. For example, in 0.123, the 3 is in the thousandth place, contributing 0.003 to the value. Rounding to the nearest thousandth means keeping three digits after the decimal point, such as 0.12345 rounding to 0.123.

Equivalently, thousandth is used in everyday measurements and quantities. One thousandth of a unit is 0.001 of that unit. In SI, the prefix milli- denotes 10^-3, from the Latin mille meaning thousand. Therefore a millimeter is one thousandth of a meter, and a milliliter is one thousandth of a liter.

The term is also used in phrases like "to the thousandth degree" or "three thousandths" to describe small proportions or angles.