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Li (unit)

Li (unit) is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Li (unit) rather than just read about it. In short: Li or ri (Chinese: 里; pinyin: lǐ, or Chinese: 市里; pinyin: shìlǐ) is a traditional Chinese unit of distance. The li has varied considerably over time but was usually about one third of an English mile and now has a standardized length of a half-kilometer (500 meters or 1,640 feet or 0.311 miles).

Li (unit) — main illustration
Li (unit) — illustration

Key takeaways

  • Li (unit) belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Li (unit) to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Li (unit) from memory before moving on to harder problems.

Reference excerpt

Li or ri (Chinese: 里; pinyin: lǐ, or Chinese: 市里; pinyin: shìlǐ) is a traditional Chinese unit of distance. The li has varied considerably over time but was usually about one third of an English mile and now has a standardized length of a half-kilometer (500 meters or 1,640 feet or 0.311 miles). This is then divided into 1,500 chi, or "Chinese feet". The character 里 combines the characters for "field" (田; tián) and "earth" (土; tǔ), since it was considered to be about the length of a single village. As late as the 1940s, a "li" did not represent a fixed measure but could be longer or shorter depending on the effort required to cover the distance. This traditional unit, in terms of historical usage and distance proportion, can be considered the East Asian counterpart to the Western league unit. However, in English league commonly means "3 miles." There is also another li (simplified Chinese: 厘; traditional Chinese: 釐; pinyin: lí) that indicates a unit of length 1⁄1000 of a chi, but it is used much less commonly. This li is used in the People's Republic of China as the equivalent of the centi- prefix in metric units, thus límǐ (厘米) for centimeter. The tonal difference makes it distinguishable to speakers of Chinese, but unless specifically noted otherwise, any reference to li will always refer to the longer traditional unit and not to either the shorter unit or the kilometer.

Changing values

Like most traditional Chinese measurements, the li was reputed to have been established by the Yellow Emperor at the founding of Chinese civilization around 2600 BC and standardized by Yu the Great of the Xia dynasty six hundred years later. Although the value varied from state to state during the Spring and Autumn period and Warring States periods, historians give a general value to the li of 405 meters prior to the Qin dynasty imposition of its standard in the 3rd century BC. The basic Chinese traditional unit of distance was the chi. As its value changed over time, so did the li's. In addition, the number of chi per li was sometimes altered. To add further complexity, under the Qin dynasty, the li was set at 360 "paces" (步; bù) but the number of chi per bu was subsequently changed from 6 to 5, shortening the li by 1⁄6. Thus, the Qin li of about 576 meters became (with other changes) the Han li, which was standardized at 415.8 meters. The basic units of measurement remained stable over the Qin and Han periods. A bronze imperial standard measure, dated AD 9, had been preserved at the Imperial Palace in Beijing and came to light in 1924. This has allowed very accurate conversions to modern measurements, which has provided a new and extremely useful additional tool in the identification of place names and routes. These measurements have been confirmed in many ways including the discovery of a number of rulers found at archaeological sites, and careful measurements of distances between known points. The Han li was calculated by Dubs to be 415.8 metres and all indications are that this is a precise and reliable determination.

Under the Tang dynasty (AD 618–907), the li was approximately 323 meters. In the late Manchu or Qing dynasty, the number of chi was increased from 1,500 per li to 1,800. This had a value of 2115 feet or 644.6 meters. In addition, the Qing added a longer unit called the tu, which was equal to 150 li (96.7 km). These changes were undone by the Republic of China of Chiang Kai-shek, who adopted the metric system in 1928. The Republic of China (now also known as Taiwan) continues not to use the li at all but only the kilometer (公里; gōnglǐ; 'common li'). Under Mao Zedong, the People's Republic of China reinstituted the traditional units as a measure of anti-imperialism and cultural pride before officially adopting the metric system in 1984. A place was made within this for the traditional units, which were restandardized to metric values. A modern li is thus set at exactly half a kilometer (500 meters). However, unlike the jin which is still frequently preferred in daily use over the kilogram, the li is almost never used. Nonetheless, its appearance in many phrases and sayings means that "kilometer" must always be specified by saying gōnglǐ in full.

Cultural use

As one might expect for the equivalent of "mile", li appears in many Chinese sayings, locations, and proverbs as an indicator of great distances or the exotic:

One Chinese name for the Great Wall is the "Ten-Thousand-Li Long Wall" (萬里長城; 万里长城; Wànlǐchángchéng). As in Greek, the number "ten thousand" is used figuratively in Chinese to mean any "immeasurable" value and this title has never provided a literal distance of 10,000 li (5,000 km or 3,100 mi). The actual length of the modern Great Wall is around 42,000 li (21,000 km or 13,000 mi), over 4 times the name's proverbially "immeasurable" length. The Chinese proverb appearing in chapter 64 of the Tao Te Ching and commonly rendered as "A journey of a thousand miles begins with a single step" in fact refers to a thousand li: 千里之行,始於足下; Qiānlǐzhīxíng, shǐyúzúxià. The greatest horses of Chinese history – including Red Hare and Hualiu (驊騮) – are all referred to as "thousand-li horses" (千里馬; qiānlǐmǎ), since they could supposedly travel a thousand li (500 km or 310 mi) in a single day. Li is sometimes used in location names, for example: Wulipu (五里铺镇), Hubei; Ankang Wulipu Airport (安康五里铺机场), Shaanxi. Sanlitun (三里屯; Sānlǐtún; 'three li village') is an area in Beijing. In Journey to the West, Sun Wukong is said to be able to travel 108,000 li in a single somersault.

Ri in Japan and Korea

… excerpt ends here. Continue reading the full article.

Illustrations

Li (unit): Map of the eastern South China Sea from 1588; each grid square is 400 li (about 133 km or 80 miles).
Map of the eastern South China Sea from 1588; each grid square is 400 li (about 133 km or 80 miles).
Li (unit): A section of the Song-era Anping Bridge in Fujian. The bridge is commonly known as the "Five-Li Bridge" due to its length.
A section of the Song-era Anping Bridge in Fujian. The bridge is commonly known as the "Five-Li Bridge" due to its length.

Worked examples

Example 1 — a first encounter with Li (unit)

Start with the simplest possible case. Write down what Li (unit) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Li (unit) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Li (unit) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Li (unit)

In research
Li (unit) appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Li (unit) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Li (unit) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chinese units of measurement, History of science and technology in China, Units of length, so understanding it makes those chapters shorter.
In everyday life
Look for Li (unit) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Li (unit) in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Li (unit) means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Li (unit) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Li (unit) in simple terms?

Li or ri (Chinese: 里; pinyin: lǐ, or Chinese: 市里; pinyin: shìlǐ) is a traditional Chinese unit of distance. The li has varied considerably over time but was usually about one third of an English mile and now has a standardized length of a half-kilometer (500 meters or 1,640 feet or 0.311 miles).

Why does Li (unit) matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Li (unit)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Li (unit).

Tags

  • Chinese units of measurement
  • History of science and technology in China
  • Units of length

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