physics

Qi

Qi is a physics 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 Qi rather than just read about it. In short: In the Sinosphere and Chinese philosophy, qi ( CHEE; simplified Chinese: 气; traditional Chinese: 氣; pinyin: qì) is a vital force traditionally believed to be a part of all living entities. Literally meaning 'vapor', 'air', 'gas', or 'breath', the word qi is polysemous, often translated as 'vital energy', 'vital force', 'material energy', or simply 'energy'.

Qi — main illustration — Qi — illustration

Key takeaways

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

Reference excerpt

In the Sinosphere and Chinese philosophy, qi ( CHEE; simplified Chinese: 气; traditional Chinese: 氣; pinyin: qì) is a vital force traditionally believed to be a part of all living entities. Literally meaning 'vapor', 'air', 'gas', or 'breath', the word qi is polysemous, often translated as 'vital energy', 'vital force', 'material energy', or simply 'energy'. Qi is also a concept in traditional Chinese medicine and in Chinese martial arts. The attempt to cultivate and balance qi is called qigong. Believers in qi describe it as a vital force, with one's good health requiring its flow to be unimpeded. Originally prescientific, today it is a pseudoscientific concept, i.e. not corresponding to the concept of energy as used in the physical sciences. Chinese gods and immortals, especially anthropomorphic gods, are sometimes thought to have qi and be a reflection of the microcosm of qi in humans, both having qi that can concentrate in certain body parts.

Linguistic aspects

The cultural keyword qì is analyzable in terms of Chinese and Sino-Xenic pronunciations. It is represented by the logographs 氣, 气, and 気 with various meanings ranging from "vapor" to "anger", and is the source of the English loanword qi or ch'i.

Pronunciation and etymology The logograph 氣 is read with two Chinese pronunciations: the usual qì 氣 "air; vital energy" and the rare archaic xì 氣 "to present food" (later disambiguated with 餼). Hackett Publishing Company, Philip J. Ivanhoe, and Bryan W. Van Norden theorize that the word qi possibly came from a term that referred to "the mist that arose from heated sacrificial offerings". Pronunciations of 氣 in modern varieties of Chinese with standardized IPA equivalents include: Standard Chinese qì /t͡ɕʰi˥˩/, Wu Chinese qi /t͡ɕʰi˧˦/, Southern Min khì /kʰi˨˩/, Eastern Min ké /kʰɛi˨˩˧/, Standard Cantonese hei3 /hei̯˧/, and Hakka Chinese hi /hi˥/. Pronunciations of 氣 in Sino-Xenic borrowings include: Japanese ki, Korean gi, and Vietnamese khí. Reconstructions of the Middle Chinese pronunciation of 氣 standardized to IPA transcription include: /kʰe̯iH/ (Bernard Karlgren), /kʰĭəiH/ (Wang Li), /kʰiəiH/ (Li Rong), /kʰɨjH/ (Edwin Pulleyblank), and /kʰɨiH/ (Zhengzhang Shangfang). Axel Schuessler's reconstruction of the Later Han Chinese pronunciation of 氣 is /kɨs/. Reconstructions of the Old Chinese pronunciation of 氣 standardized to IPA transcription include: */kʰɯds/ (Zhengzhang Shangfang), */C.qʰəp-s/ (William H. Baxter and Laurent Sagart), and */kə(t)s/ (Axel Schuessler). The etymology of qì interconnects with Kharia kʰis "anger", Sora kissa "move with great effort", Khmer kʰɛs "strive after; endeavor", and Gyalrongic kʰɐs "anger".

Characters In the East Asian languages, qì has three logographs:

氣 is the traditional Chinese character, Korean hanja, and Japanese kyūjitai ("old character form") kanji 気 is the Japanese shinjitai ("new character form") kanji 气 is the simplified Chinese character. In addition, qì 炁 is an uncommon character especially used in writing Daoist talismans. Historically, the word qì was generally written as 气 until the Han dynasty (206 BCE–220 CE), when it was replaced by the 氣 graph clarified with mǐ 米 "rice" indicating "steam (rising from rice as it cooks.)" and depicting the Traditional Chinese view of the transformative, changeable nature of existence and the universe. This primary logograph 气, the earliest written character for qì, consisted of three wavy horizontal lines seen in Shang dynasty (c. 1600–1046 BCE) oracle bone script, Zhou dynasty (1046–256 BCE) bronzeware script and large seal script, and Qin dynasty (221–206 BCE) small seal script. These oracle, bronze, and seal scripts logographs 气 were used in ancient times as a phonetic loan character to write qǐ 乞 "plead for; beg; ask" which did not have an early character. The vast majority of Chinese characters are classified as radical-phonetic characters. Such characters combine a semantically suggestive "radical characters" with a phonetic element approximating ancient pronunciation. For example, the widely known word dào 道 "the Dao; the way" graphically combines the "walk" radical 辶 with a shǒu 首 "head" phonetic. Although the modern dào and shǒu pronunciations are dissimilar, the Old Chinese *lˤuʔ-s 道 and *l̥uʔ-s 首 were alike. The regular script character qì 氣 is unusual because qì 气 is both the "air radical" and the phonetic, with mǐ 米 "rice" semantically indicating "steam; vapor". This qì 气 "air/gas radical" was only used in a few native Chinese characters like yīnyūn 氤氲 "thick mist/smoke", but was also used to create new scientific characters for gaseous chemical elements. Some examples are based on pronunciations in European languages: fú 氟 (with a fú 弗 phonetic) "fluorine" and nǎi 氖 (with a nǎi 乃 phonetic) "neon". Others are based on semantics: qīng 氫 (with a jīng 巠 phonetic, abbreviating qīng 輕 "light-weight") "hydrogen (the lightest element)" and lǜ 氯 (with a lù 彔 phonetic, abbreviating lǜ 綠 "green") "(greenish-yellow) chlorine". Qì 氣 is the phonetic element in a few characters such as kài 愾 "hate" with the "heart-mind radical" 忄or 心, xì 熂 "set fire to weeds" with the "fire radical" 火, and xì 餼 "to present food" with the "food radical" 食. The first Chinese dictionary of characters, the Shuowen Jiezi(121 CE) notes that the primary qì 气 is a pictographic character depicting 雲气 "cloudy vapors", and that the full 氣 combines 米 "rice" with the phonetic qi 气, meaning 饋客芻米 "present provisions to guests" (later disambiguated as xì 餼).

Meanings Qi is a polysemous word. The unabridged Chinese-Chinese character dictionary Hanyu Da Cidian defines it as "present food or provisions" for the xì pronunciation but also lists 23 meanings for the qì pronunciation. The modern ABC Chinese-English Comprehensive Dictionary, which enters xì 餼 "grain; animal feed; make a present of food", and a qì 氣 entry with seven translation equivalents for the noun, two for bound morphemes, and three equivalents for the verb. n. ① air; gas ② smell ③ spirit; vigor; morale ④ vital/material energy (in Ch[inese] metaphysics) ⑤ tone; atmosphere; attitude ⑥ anger ⑦ breath; respiration b.f. ① weather 天氣 tiānqì ② [linguistics] aspiration 送氣 sòngqì v. ① anger ② get angry ③ bully; insult.Qi was also thought of as meaning "'forces in nature'" that deity could control and magicians and occultists could harness.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Qi

Start with the simplest possible case. Write down what Qi claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, 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 Qi 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 Qi 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 Qi

In research: Qi appears in physics 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 Qi 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: Qi is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aikido, Chinese martial arts terminology, Concepts in Chinese folk religion, so understanding it makes those chapters shorter.
In everyday life: Look for Qi 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 Qi in 20 minutes

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

Frequently asked questions

What is Qi in simple terms?

Why does Qi matter?

Because it connects several physics 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 Qi?

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 Qi.

Qi