Effects of the storage conditions on the stability of natural and synthetic cannabis in biological matrices for forensic toxicology analysis: An update from the literature

Cun
Wooden ruler of the western Han dynasty, unearthed at Jinguan Pass Site in Jinta County
General information
Unit system	Chinese unit
Unit of	length
Conversions
1 cun in ...	... is equal to ...
metric (SI) units	⁠1/30⁠ m  ~33.33 mm
imperial/US units	~0.10936 ft  ~1.3123 in

Tsun
A section of an old Hong Kong ruler, showing the last (10th) cun of a chi. One can see that the chi in that jurisdiction was exactly equal to ⁠14+5/8⁠ of an inch. A metric ruler is shown next to it for comparison.
General information
Unit system	Chinese unit
Unit of	length
Conversions
1 tsun in ...	... is equal to ...
metric (SI) units	0.0371475 m  ~37.15 mm
imperial/US units	0.121875 ft  ⁠1+37/80⁠ in

A cun (Chinese: 寸 ts'wun; Pinyin cùn IPA |mi=[tsʰwə̂n]), often glossed as the Chinese inch, is a traditional Chinese unit of length. Its traditional measure is the width of a person's thumb at the knuckle, whereas the width of the two forefingers denotes 1.5 cun and the width of four fingers (except the thumb) side-by-side is 3 cuns.^[1] It continues to be used to chart acupuncture points on the human body, and, in various uses for traditional Chinese medicine.

The cun was part of a larger decimal system. A cun was made up of 10 fen, which depending on the period approximated lengths or widths of millet grains,^[2] and represented one-tenth of a chi ("Chinese foot").^[3] In time the lengths were standardized, although to different values in different jurisdictions. (See Chi (unit) for details.)

In Hong Kong, using the traditional standard, it measures ~3.715 cm (~1.463 in) and is written "tsun".^[4] In the twentieth century in the Republic of China, the lengths were standardized to fit with the metric system, and in current usage in People's Republic of China and Taiwan^{[citation needed]} it measures ⁠3+1/3⁠ cm (~1.312 in).

In Japan, the corresponding unit, sun (寸), was standardized at 1000⁄33 mm (3.03 cm, ~1.193 in, or ~0.09942 ft).

• shaku

• Cun measurements