公 | gōng

In Mandarin Chinese, 公 (Pinyin: gōng 🔊) is an extremely common word with many meanings. As an adjective, it can mean “public”, “communal”, “general”, “international”, “fair” and, when applied to animals, “male”:

• 公 + 牛 = 公牛 (gōngniú 🔊): bull
• 公 + 羊 = 公羊 (gōngyáng 🔊): ram
• 公 + 鸡 = 公鸡 (gōngjī): cockerel, rooster

Could it be that “male” is a “general” kind of animal, as opposed to a female animal which is special?

As a noun, 公 can mean “official business”, “authorities” or “duke”. It is also used as a SI prefix kilo- as in 公斤 (gōngjīn) “kilogram” and 公里 (gōnglǐ) “kilometre”. 公公 (gōnggong) means “father-in-law” (more precisely, husband’s father).

There are several theories of this character’s origin. According to Wiktionary,

The traditional interpretation as given by Han Feizi is that 公 is a compound of 八 [= 背 (“to deviate; opposite”)] and 厶 [original form of 私 (“individual; private”)], i.e. the opposite of “individual”; public. This theory is supported by Sun Yirang and Qiang Kaiyun, despite the somewhat different shape of the top component from 厶.

This is disputed in modern times by Gao Hongjin, who thinks that the 八 on top stands for 分 (“to divide; to distribute”) and the bottom round component of 口 symbolises the general object. 公 thus represents “equally dividing resources so that they are communal”.

Another theory put forth by Zhu Fangpu is that 公 is a pictogram, being the original form of 瓮 (“a wide-mouthed round-bottomed jar”), and later borrowed for the meaning of “public”.

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太 | tài

In Mandarin Chinese, 太 (Pinyin: tài 🔊) is used either as an adverb “so”, “too”, “very”, or an adjective meaning “greatest”, “highest”, “noble”, “senior”, “utmost” etc. 太 is extremely common: “is one of the 1000 most commonly used words” in the Collins Chinese Dictionary. There are many compound words starting with 太, such as 太平 (tàipíng) “peace and tranquility”, 太空 (tàikōng) “space”, 太太 (tàitai) “wife”, or 太爷爷 / 太爺爺 (tàiyéye) “great-grandfather”.

By now we’ve got used to the figurative meanings of Chinese numerals (e.g. 万 means “ten thousand” but also “all”, “countless” and so on). Well, in case of 太 the opposite seems to be true as well: in Mainland China, 太 is employed as prefix “tera-” (10¹²), as in 太字节 / 太字節 (tàizìjié) “terabyte”.

Just like now-familiar 犬 “dog”, 太 consists of 大, “big”, modified with a stroke 丶; however in the case of 太 the stroke moved from the presumed “ear” position to somewhere, er, between the “legs”.

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亿 | yì

In Mandarin Chinese, 亿 (Pinyin: yì 🔊) is a word for “hundred million” (i.e. 10⁸) as well as, you may have guessed by now, “many”.

Alternative way of expressing the number 100 000 000 is 万万 / 萬萬 (wànwàn), i.e. 万 (wàn) “ten thousand” squared. However, 万万 is more often used as an adverb meaning “absolutely” or “certainly” (not).

亿 is a simplified form of the traditional hanzi 億. It is a phono-semantic compound of 亻, a radical form of our old friend 人 (“people”) and phonetic 意 (yì), which later got replaced by totally unrelated but similarly-sounding 乙 (yǐ). It looks like even in ancient times in China there was a firm association between “people” and “many” although, curiously, some historical forms of this character lack the radical 亻.

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兆 | zhào

In Mandarin Chinese, 兆 (Pinyin: zhào) is a word for “sign” or “omen”. In Mainland China, it also means “million” (i.e. 10⁶), as in 兆瓦 (zhào wǎ), “megawatt”. However, in Japanese the very kanji 兆 stands for “trillion”, i.e. “million million” (this meaning is now obsolete in Mainland China).

Alternative, and less ambiguous, way of expressing the number 10⁶ is 百万 / 百萬 (bǎiwàn), that is, 百 “hundred” by 万 “ten thousand”. Alternative way of expressing the number 10¹² is 亿万 / 億萬 (yìwàn), i.e. 亿 (10⁸) by 万 (10⁴). In Mainland China, 太 (tài) is used as prefix “tera-” (10¹²).

According to Uncle Hanzi, 兆 originally represented “the cracks in oracle bones caused by fire which were thought to be signs (omens) of the future”.

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ψ | psi

The letter ψ (psi) was yet another Greek addition to the alphabet, placed after the letters of Phoenician origin, along with φ, χ and ω. According to Wikipedia,

The letter’s origin is uncertain. It may or may not derive from the Phoenician alphabet. It appears in the 7^th century BC, expressing /ps/ in the Eastern alphabets, but /kʰ/ in the Western alphabets (the sound expressed by Χ in the Eastern alphabets).

The letter ψ has a number of uses in maths and sciences, including

• in biochemistry: pseudouridine
• in carotenoid nomenclature: acyclic end group. For example, lycopene is ψ,ψ-carotene.
• in hydrostatics and biology: water potential
• in fluid mechanics: stream function
• in mathematics: the division polynomials ψ_n
• in mathematics: the polygamma function
• in mathematics: the reciprocal Fibonacci constant with approximate value of 3.35989
• in molecular biology: the ψ packaging element
• in particle physics: the J/ψ meson (psion)
• in protein chemistry: one of three dihedral angles (φ, ψ and ω) in a protein chain
• in quantum mechanics: wave function

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χ | chi

The letter χ (chi) was a Greek addition to the alphabet, placed after the letters of Phoenician origin, along with φ, ψ and ω. According to Wikipedia,

In Ancient Greek, ‘Χ’ and ‘Ψ’ were among several variants of the same letter, used originally for /kʰ/ and later, in western areas such as Arcadia, as a simplification of the digraph ‘ΧΣ’ for /ks/. In the end, more conservative eastern forms became the standard of Classical Greek, and thus ‘Χ’ (Chi) stands for /kʰ/ (later /x/). However, the Etruscans had taken over ‘Χ’ from western Greek, and it therefore stands for /ks/ in Etruscan and Latin.

The Greek χ gave rise to the Latin X, Gothic enguz 𐍇 and Cyrillic Х.

The lower-case χ has a number of uses in maths and sciences:

• in biology: Chi site or χ site, a DNA sequence that serves as a recombination hot spot (“Chi” is an abbreviation of “crossover hotspot instigator”)
• in chemistry: electronegativity
• in graph theory: chromatic number χ(G) for a graph G
• in mathematics: the Euler–Poincaré characteristic of a surface
• in statistics: χ² or chi-square
• in thermodynamics: a free energy parameter known as the χ-parameter, employed in the Flory–Huggins solution theory

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μ | mu

The Greek letter μ (mu) arose from the ancient Phoenician letter 𐤌 (mēm) which, in turn, was derived from the Egyptian hieroglyph for water, 𓈖.

The lower-case μ has many uses in maths, engineering and sciences, for example:

• in coordination chemistry: μ-, a prefix for a bridging ligand
• in electromagnetism:
  • the magnetic moment and the units to express it, such as the Bohr magneton μ_B and the nuclear magneton μ_N
  • the permeability µ, measured in henries per meter (H·m⁻¹);
  • the vacuum permeability or magnetic constant µ₀, which has the exact value of 4π×10⁻⁷ H·m⁻¹
• in fluid mechanics: dynamic viscosity
• in mathematics: the Möbius function μ(n)
• in maths and physics: µ (micro-), a unit prefix in the metric system for 10⁻⁶ (one millionth)
• in particle physics: muon μ⁻ and antimuuon μ⁺ (formerly called μ-mesons)
• in pharmacology: μ-opioid receptor (MOR)
• in physics: the coefficient of friction
• in physics: the electrical_mobility of a charged particle
• in thermodynamics: chemical potential aka partial molar free energy μ_i

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: | ː

The colon (:) is a punctuation mark used in many ways:

• to introduce lists (like this one)
• before a definition
• before a description
• to make explicit or expand on something, as exemplified on the following line:
• in Finnish and Swedish: to indicate possession (playing the role similar to that of the apostrophe in English)
• before an explanation or an example, as shown on the following line
• to form contractions, as in Swedish: Thomas Gustafsson can be abbreviated as Thomas G:son
• before direct speech or quotations. For example, Wikipedia says:

  In British English, it was once common for a colon to be followed by a hyphen or dash to indicate a restful pause, in a typographical construction known as the “dog’s bollocks”, though this usage is now discouraged.

• to introduce spoken words in written dialogues
• to separate a title and subtitle of a work when written the same line
• in American English: in formal letter writing
• to separate hours:minutes:seconds when written in numbers
• to separate chapter:verse in Biblical citations
• in mathematics and elsewhere to indicate a ratio or a scale
• in a variety of other ways in mathematics
• in certain O:B:Sc:U:Re ways in chemical nomenclature
• in many ::wonderful ways:: in C:\omputing

A triangular colon (ː) is used in International Phonetic Alphabet to mark /mɑːk/ the preceding sound as “long”.

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. | 。

The full stop or period (.) is a punctuation mark typically found at the end of a sentence, unless it is a question or exclamation.

In the 3^rd century BC, the Greeks developed a punctuation system where ὑποστιγμή (the low dot .) functioned as the modern comma, while στιγμὴ μέση (the interpunct or the middle dot ·) played the role similar to that of the modern semicolon; στιγμὴ τελεία (the high dot ˙) marked the end of a completed thought, like the modern full stop.

Classical Latin had no lower-case letters, interword spacing or punctuation; hovvever·the·interpvnct·vvas·sometimes·vsed·to·separate·vvords

Apart from the ends of sentences, full stops are found after initials, some abbreviations and acronyms. In English-speaking countries, they indicate a decimal point, although in Britain until 1970s they used the interpunct for this purpose.

In Chinese and Japanese, a small circle 。 is used to indicate the end of sentence instead of a solid dot .

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υ | upsilon

The Greek letter υ (upsilon) was derived from the ancient Phoenician letter 𐤅 (wāw) which meant “hook”. This letter is the most prolific of all Greek alphabet: it gave rise to the Latin letters F, U, V, Y, W as well as Cyrillic Ѵ and У. In the same time, as its upper case Υ is too similar to the Latin Y and lower case too similar to the Latin u and v, it does not make a good mathematical or scientific symbol. In the International Phonetic Alphabet, the lower-case υ is used to represent a labiodental approximant, as in Finnish veli /ˈʋeli/ or Norwegian Stavanger /stɑˈʋɑŋər/.

The letter ʊ (Latin upsilon) was derived from the Greek lower-case υ. It is used in the IPA to represent a near-close near-back rounded vowel, as in English put /pʊt/ or German kurz /kʊrts/.

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τ | tau

The Greek letter τ (tau) was derived from the ancient Phoenician letter 𐤕 (tāw) which, in turn, was derived from an Egyptian hieroglyph ✕ meaning “mark”.

The lower-case τ has many uses in maths, engineering and sciences, such as

• in biochemistry: the τ protein, a protein that stabilise microtubules
• in continuum mechanics: shear stress
• in differential geometry: torsion of a curve
• in engineering and physics: the time constant of a system
• in geometry: the tortuosity
• in mathematics: the Ramanujan tau function, an irrational number with approximate value of 0.41468
• in mechanics: the torque, aka moment of force
• in optics: optical depth of a material, defined as τ = −ln T, where T is the transmittance of that material
• in particle physics: tauon τ⁻ and antitauon τ⁺
• in physical sciences: relaxation time
• in physics: the lifetime of a spontaneous emission process
• in relativity: proper time
• in spectroscopy: rotational correlation time
• in statistics: the Kendall rank correlation coefficient

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ω | omega

The letter ω (omega) is the 24^th and last letter of the Greek alphabet. It was first introduced in the 7^th century BC as a broken-up at the side variant of omicron. This letter was adopted into the early Cyrillic alphabet as Cyrillic omega (Ѡ, ѡ), with both upper- and lower-case letters similar to the Greek lower-case ω.

The lower-case ω has quite a few uses in maths, engineering and sciences, for example

• in astronomy: the argument of periapsis of an orbit
• in biochemistry: to denote the carbon atom furthest from the carboxyl group of a fatty acid. “ω−i fatty acid” is an unsaturated fatty acid with a double bond (C=C) at the i^th carbon atom from the end, as in ω−3 fatty acids, ω−7 fatty acids, etc.
• in electrical circuits: natural frequency ω₀
• in molecular biology: the smallest subunit of RNA polymerase
• in number theory: ω(n), the number of distinct prime factors of n
• in particle physics: omega meson
• in physics: angular frequency and angular velocity
• in protein chemistry: one of three dihedral angles (φ, ψ and ω) in a protein chain. ω is usually restricted to be 180° (trans) or 0° (cis).

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ρ | rho

The Greek letter ρ (rho) was derived from the ancient Phoenician letter 𐤓 (rēš), which is thought to have come from a pictogram of a head. As a numeral, ρ has a value of 100. Incidentally, this is our 100^th post.

The lower-case ρ (or its variant ϱ) has many uses in maths and sciences, such as:

• in electrical engineering and physics: resistivity (the reciprocal of conductivity σ)
• in electromagnetism: the volume charge density, ρ_q
• in molecular biology: the ρ factor, a protein involved in the termination of transcription
• in mathematics: the Dickman–de Bruijn function ρ(u)
• in mathematics: the plastic number, a constant with approximate value of 1.32472, the unique real solution of the cubic equation x³ = x + 1
• in mathematics: the prime constant, an irrational number with approximate value of 0.41468
• in mathematics: ρ(A), the spectral radius of a matrix A
• in organic chemistry: ρ-value (the reaction constant) of the Hammett equation
• in particle physics: rho mesons ρ⁺, ρ⁰ and ρ⁻
• in physics: mass density and air density
• in spectroscopy: rotational relaxation time
• in statistics: the Pearson correlation coefficient

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ξ | xi

The Greek letter ξ (xi) was derived from the ancient Phoenician letter 𐤎 (sāmek), which, in its turn, could have evolved from the Egyptian hieroglyph 𓊽 (djed), representing the spinal column. Other theories say 𐤎 meant “fish” (actually showing a fish skeleton?) or “a tent peg”.

The lower-case ξ has a number of uses in maths and sciences, including

• in astronomy: the correlation function ξ(r)
• in natural product chemistry: to denote unknown configuration (which could be either α or β) at a chiral centre
• in mathematics: the remainder term of Taylor’s theorem
• in physical chemistry: the extent of reaction
• in physics: the spatial frequency (the reciprocal of the wavelength λ)

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♯ | sharp

In musical notation, ♯ is a symbol for sharp (dièse) which is commonly found as an accidental or in key signatures. According to Wikipedia,

The modern accidental signs derive from the two forms of the lower-case letter b used in Gregorian chant manuscripts to signify the two pitches of B, the only note that could be altered. The “round” b became the flat sign, while the “square” b diverged into the sharp and natural signs.

They say that ♯ must not be confused with the # sign variously known as “hash”, “number sign” or “pound sign”. The truth is, there is very little scope for confusion of ♯ with # since ♯ is only used in the musical context. In fact, in pre-Unicode era, # was exactly the symbol for sharp (and lower-case b for flat) that was used in ASCII text files, and nobody would interpret F# as anything but F♯. On the contrary, there is every chance of confusion if you use it either as a number or pound sign. Personally, I resent these two uses. I mean, you must be really lazy to use # instead of № or No. As for “pound”, hello? Write lb. or switch to the metric system like the rest of the world.

If you really need to know the difference, look at the pictures. The sharp has two vertical chili peppers crossed by two slanted parallel peppers that rise from left to right. In this fashion, the slanted peppers won’t interfere with the staff lines. The hash has two horizontal peppers crossed by two slightly slanted parallel peppers.

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σ | sigma

The Greek letter σ (sigma) was derived from the ancient Phoenician letter 𐤔 (šīn) which meant “tooth”.

ς is the lower-case letter sigma (σίγμα τελικό) when used as the final letter in a word.

The lower-case σ has been widely adopted in maths and sciences, for instance:

• in chemistry: the σ bonds
• in continuum mechanics: the Cauchy stress tensor σ
• in biochemistry: σ factor of RNA polymerase
• in mathematics: σ(z; Λ), the Weierstrass sigma function
• in organic chemistry: σ-value (the substituent constant) of the Hammett equation
• in particle physics: cross section
• in pharmacology: the σ–receptors
• in physics: the surface charge density, σ_q
• in physics: a symbol for conductivity (the reciprocal of resistivity ρ)
• in statistics: the standard deviation
• in thermodynamics: the Stefan–Boltzmann constant

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λ | lambda

The Greek letter λ (lambda) was derived from the ancient Phoenician letter 𐤋 (lāmed) which meant “goad” (a cattle prod).

The lower-case letter λ has many uses in maths, engineering and sciences, including:

• in biology: coliphage λ
• in engineering, mathematics and physics: the wavelength
• in mathematical logic: λ-calculus
• in organic chemistry: λ-convention for non-standard valence states
• in immunology: a type of the immunoglobulin light chain
• in linear algebra: an eigenvalue
• in nuclear physics: the exponential decay constant
• in physics: the linear charge density, λ_q

λ is also one of the international symbols for LGBT rights.

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κ | kappa

The Greek letter κ (kappa) was derived from the ancient Phoenician letter 𐤊 (kāp) which meant “palm” (of a hand).

The lower-case κ is pretty much just a smaller version of the upper-case Κ and is virtually indistinguishable from the upper-case Roman K as well as the Cyrillic К/к. I prefer using the cursive ϰ.

The lower-case κ and/or cursive ϰ have quite a few uses in maths, engineering and sciences, for instance:

• in coordination chemistry: a symbol for denticity
• in geometry: kappa curve, or Gutschoven’s curve, a two-dimensional curve resembling the letter ϰ
• in electrical engineering: conductivity (the reciprocal of resistivity ρ)
• in fluid dynamics: the von Kármán constant
• in immunology: a type of the immunoglobulin light chain
• in mathematics and physics: the curvature
• in pharmacology: κ-opioid receptor (KOR)
• in statistics: Cohen’s kappa coefficient

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ι | iota

The Greek letter ι (iota) was derived from the ancient Phoenician letter 𐤉 (yōd) which meant “arm”. The archaic Cyrillic iota ꙇ looks exactly the same.

The lower-case ι looks too similar to the Latin letters i and l to be widely used as a symbol on its own. Still, it has been adopted in maths and sciences, for instance:

• in biochemistry: ι-toxin, a pore forming toxin from Clostridium perfringens
• in mathematical logic: a definite description operator
• in natural product chemistry: ι-carrageenan, a polysaccharide extracted from red algae that gels in the presence of calcium ions

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〇 | líng

In Mandarin Chinese, 〇 (Pinyin: líng 🔊) is a word for number zero.

In AD 690, Wu Zetian (624—705), the only Empress Regnant in the history of China, adopted a number of new characters, one of which was 〇. Originally, it was meant to replace the unwieldy character 星 “star”. After the Empress’s death, the new characters fell into disuse. In 1247, Qin Jiushao (ca. 1202—1261) found a new job for 〇. It was introduced as the symbol for zero in his work 數書九章 (Shùshū Jiǔzhāng, “Mathematical Treatise in Nine Sections”). Another hanzi with the same meaning, 零, is mainly used for financial purposes.

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