Yarn numbering is a term used to describe a yarn's physical size,
or more specifically,
its linear density.
Since short-stable spun yarns, like those containing cotton,
can vary greatly in their bulk,
measuring a yarn's diameter in a consistent way
can be almost impossible.
For this reason,
it is necessary to employ a more precise way of describing a yarn's physical size.
There are two main methods for assigning a yarn number.
One method is called the direct yarn numbering system.
In this method,
the yarn's linear density is denoted as a weight to length ratio.
This method is commonly used for synthetic or man-made, fiber.
For example,
a 70-denier yarn means that there are 70 grams per 9000 meters.
Denier is just one of the direct yarn numbering units,
but it is one of the more common direct units used for synthetics.
The other method for describing a yarn's
linear density is called the indirect method.
In this method,
the yarn size is described in length to weight units.
For cotton yarns,
it's typical to see the denotations NCC, or sometimes NE.
These denotations are otherwise known as cotton count or number English.
For example,
a number English 30 single,
100% cotton or blend yarn
means 30 times 840 yards per pound.
840 yards is known as a hank.
When all this is said,
it's important to realize that there are other
yarn numbering units that may be encountered.
It's impossible to cover all of them.
This is especially true in China and some other foreign
countries, where many variations of yarn numbering may have evolved.
Be aware that not everyone speaks or even
knows all of these terms and their relationships.