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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𝄢 | F-clef

The F-clef is named so because the line passing between the two dots corresponds to the note F. The symbol 𝄢 evolved from the Latin letter “F”, its two horizontal strokes reduced to dots.

To me, 𝄢 is a more elegant symbol than 𝄞 (G-clef). The dots aside, 𝄢 looks very much like a golden spiral, i.e. a spiral whose growth factor is the golden ratio 𝜑. This inspired me to make the F-clef from an old gold-plated guitar string:

When placed on the fourth line of the stave, 𝄢 is called the bass clef. The bass clef is the only F-clef in modern use.

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𝄞 | G-clef

In musical notation, a clef provides the reference point for the notes on the stave. For example, the G-clef is named so because the line passing through its curl corresponds to the note G. The fancy symbol 𝄞 evolved from the Latin letter “G”.

When placed on the second line of the stave, 𝄞 is called the treble clef. Its Russian name is скрипичный ключ because the music for violin (скрипка) is written in treble clef. This is the most commonly used clef today. No wonder this symbol grew to represent music in general — much to the chagrin of bass players.

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♮ | natural

In musical notation, ♮ is a symbol for natural, an accidental used to cancel a flat or sharp from either a preceding note or the key signature. Like the sharp sign ♯, the natural sign is derived from a “square” b used to denote B♮ in Gregorian chant manuscripts.

In Russian musical slang, бекар (from French bécarre) stands for delay or cancellation of an event, a failure to fulfill promises etc.; the derived verbs бекарить and забекарить mean “to cancel”, “to skip”, or “be late”.

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♭ | flat

In musical notation, ♭ is a symbol for flat (bemol) which is commonly found as an accidental or in key signatures. The symbol is derived derived from a stylised lower-case b, “b rotundum”.

In Russian musical slang, бемоль means “belly”.

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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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0 | zero

Probably the first documented use of a number zero in the Old World was by Claudius Ptolemy in the Almagest (ca. 130 AD), although in the Americas the concept and symbol for zero existed much earlier.

Ptolemy employed the symbol ο̄ (“Hellenistic zero”) within a Babylonian sexagesimal numeral system. The oldest known mention of zero and the decimal positional system are found in the Jainist cosmological text Lokavibhāga (AD 458). By the 11^th century, the Hindu–Arabic numeral system, complete with zero, reached Europe.

In my handwriting, I almost always write this digit as a slashed zero, 0.

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θ | theta

The Greek letter θ (theta) was derived from the ancient Phoenician letter 𐤈 (ṭēt) which meant “wheel”. The Cyrillic letter Ѳ (fita), derived from θ, was a part of the Russian alphabet until 1918. Gogol wrote in a footnote to Dead Souls:

«Ѳетюкъ — слово обидное для мужчины, происходитъ отъ Ѳ, буквы, почитаемой нѣкоторыми неприличною буквою.»

(“Thetuk” is an offensive word to a man, it comes from Ѳ, a letter thought by some indecent.)

Speaking of decency: according to Real Academia Española, this letter should be called zeta, perhaps to avoid using the word teta, while the letter ζ is supposed to be called dseta.

The lower-case letter θ has quite a few uses in maths and sciences, for instance:

• in astronomy, geography, mathematics and physics: one of the coordinates in spherical coordinate system (r, θ, φ)
• in neurophysiology: θ-waves, a type of brain waves detected by electroencephalography
• in linguistics: θ-role
• in mathematics: a number of different fuctions called theta functions
• in particle physics: symbol for theta meson
• in phonetics: voiceless dental fricative, as in theta /ˈθiːtə/ or /ˈθeɪtə/
• in thermodynamics: a symbol for potential temperature

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网 | wǎng

In Mandarin Chinese, 网 (Pinyin: wǎng 🔊) means “net” or “web”. Note the tonal difference between 网 and 王 (wáng). Naturally, nowadays this word has acquired the modern meaning of “network”, as in information or communication network. Rather unsurprisingly, 网 is short for 互联网 (Hùliánwǎng), “the Internet”.

网 is a simplified form of 網. In this particular case, the simplified character makes more sense than a traditional one — I don’t know what exactly the ancient Chinese had in mind but I like to think of 网 as a doodle of a goal net.

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η | eta

The Greek letter η (eta) was derived from the ancient Phoenician letter 𐤇 (ḥēt) which, in turn, was derived from an Egyptian hieroglyph of courtyard, 𓉗.

The lower-case letter η has quite a few uses in maths, engineering and sciences, for instance:

• in coordination chemistry: a symbol for hapticity
• in cosmology: the baryon–photon ratio
• in mathematics: the Dedekind eta function η(τ), the Dirichlet eta function η(s), and the Weierstrass eta function η(w; Λ)
• in particle physics: symbols for eta meson (η), eta prime meson (η′), charmed eta meson (η_c) and bottom eta meson (η_b)
• in rheology: a symbol for viscosity

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ζ | zeta

The Greek letter ζ (zeta) was derived from the ancient Phoenician letter 𐤆 (zayin) which meant “sword” or some other weapon.

In the system of Greek numerals, the letters α to ε have the respective values 1 through 5. Bizarrely, ζ has the value of 7. This may account for the fact that chemists don’t like using Greek letters beyond ε when numbering the atoms in the chain. Still, the lower-case letter ζ has some uses in maths and sciences, for example:

• in colloidal chemistry: ε_i, ζ-potential, the electrokinetic potential of colloidal dispersions
• in mathematics: ζ(s), the Euler–Riemann zeta function
• in mathematics: ζ(z; Λ), the Weierstrass zeta function
• in pharmacology: ζ-opioid receptor, aka opioid growth factor receptor

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花 | huā

In Mandarin Chinese, the literal meaning of 花 (Pinyin: huā 🔊) is “flower”. This word has many figurative meanings, such as “pattern” (floral or otherwise), “pinnacle”, “fireworks”, “a beauty” or “a lady of the night”. 花 forms many compounds, such as 茶花 (cháhuā) “camellia”, 火花 (huǒhuā) “spark” and 水花 (shuǐhuā) “spray”.

The top part of this character, 艹, means “grass”. We’ve seen this radical before as a part of 茶 (chá), “tea”. The bottom part, 化 (huà), in its turn, consists of two 人, i.e. “people”: one upright (亻) and another upside down, together symbolising “change” or “reversal”. According to Ponte Ryūrui,

The bottom part of 花 (化, か, i.e. “action of making something”, “change”) acts purely phonetically, although certain etymology theories suggest to take 化 as “a change” of the state of a plant (blossoming).

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ε | epsilon

The Greek letter ε (epsilon) was derived from the ancient Phoenician letter 𐤄 (hē) which meant “window”. In its turn, ε gave rise to the Latin e and a number of other letters.

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

• in analytical chemistry: ε_i, molar attenuation coefficient, also known as the molar extinction coefficient and molar absorptivity
• in astronomy: the fifth brightest star in a constellation. For instance, Alnilam is designated as ε Orionis.
• in calculus: (ε, δ)-definition of limit
• in medicine: ε-wave, a feature of electrocardiograms of many arrhythmogenic right ventricular dysplasia (ARVC) patients
• in organic chemistry: ε, the fifth atom in a chain when counting from a functional group. The names such as ε-aminocaproic acid make use of this nomenclature.
• in phonetics: Latin epsilon, ɛ, representing the open-mid front unrounded vowel, as in epsilon /ɛpˈsaɪ.lən/ or /ˈɛp.sɪˌlɒn/
• in physics: ε₀, vacuum permittivity constant

α through ɛ appears to be the extent to which most people know the letter sequence of the Greek alphabet.

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δ | delta

The Greek letter δ (delta) was derived from the ancient Phoenician letter 𐤃 (dālet) which, in turn, was derived from 𓉿, an Egyptian hieroglyph depicting a door.

The lower-case letter δ has many uses in maths and sciences, such as:

• in astronomy: the fourth brightest star in a constellation. For instance, Mintaka is designated as δ Orionis.
• in chemistry: δ bond, a type of covalent chemical bond formed by overlapping lobes of d orbitals
• in chemistry: a symbol for partial charge, δ− or δ+
• in earth sciences: to express stable isotope ratios, for example δ²H, δ¹³C, δ¹⁸O
• in mathematics: δ, the first Feigenbaum constant (approximately 4.669201)
• in maths and science: Dirac δ function
• in neurophysiology: δ-waves, a type of brain waves detected by electroencephalography
• in pharmacology: a type of opioid receptor
• in thermodynamics: inexact differential. For example, the first law of thermodynamics is expressed as

  dU = δQ – δW

  where U is internal energy, Q is heat and W is work.

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γ | gamma

The Greek letter γ (gamma) was derived from the ancient Phoenician letter 𐤂 (gīml). One theory says that it represented a throwing stick, another links it to (an image of) a camel.

The lower-case letter γ has a number of uses in maths and sciences, for example:

• in astronomy: the third brightest star in a constellation. For instance, Bellatrix is designated as γ Orionis.
• in inorganic chemistry: a symbol for certain allotropes, for example γ-iron (austenite) or γ-sulfur
• in mathematics: the Euler—Mascheroni constant, a mathematical constant with approximate value of 0.57721
• in organic chemistry: γ-carbon, the third carbon atom in a chain when counting from a functional group. The names such as γ-aminobutyric acid (GABA) make use of this nomenclature.
• in neurophysiology: γ-waves, a type of brain waves detected by electroencephalography
• in phonetics: voiced velar fricative (IPA symbol ɣ)
• in physics: γ is the symbol for a photon, probably derived from γ-rays or γ-radiation, a kind of electromagnetic radiation arising from the radioactive decay (γ-decay)
• in special relativity: Lorentz factor

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β | beta

The Greek letter β (beta) was derived from the ancient Phoenician letter 𐤁 (bet). The word alphabet originates from the Greek ἀλφάβητος (alphabētos), from ἄλφα (“alpha”) + βῆτα (“beta”).

The lower-case letter β has found many uses in maths and sciences:

• in astronomy: the second brightest star in a constellation. For instance, Rigel is designated as β Orionis
• in biochemistry: β-sheet, a type of protein secondary structure
• in biology: β cell, a type of cell found in the pancreatic islets of the pancreas. The primary function of a β cell is to produce insulin.
• in inorganic chemistry: a symbol for certain allotropes, for example β-tetragonal boron, β-germanium, and β-tin
• in mathematics: β(s), the Dirichlet beta function
• in natural product chemistry: a stereodescriptor used in a number of different ways
• in nuclear physics: beta particle, a high-energy electron (β⁻) or positron (β⁺) emitted in the radioactive decay; β-decay is a radioactive process in which an atomic nucleus emits an β-particle
• in organic chemistry: β-carbon, the second carbon atom in a chain when counting from a functional group
• in pharmacology: β₁, β₂ and β₃, subtypes of adrenergic receptors
• in phonetics: voiced bilabial fricative (IPA symbol β)
• in special relativity: a symbol for the speed of an object relative to the speed of light: β = v/c
• in thermodynamics and fluid mechanics: a symbol for compressibility
• in zoology: β animals, which often act as second-in-command to the reigning α-males and/or α-females

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α | alpha

The Greek letter α (alpha) was derived from the ancient Phoenician letter 𐤀 (ʾālep) which, in turn, was derived from 𓃾, the Egyptian hieroglyph of an ox’s head.

The lower-case letter α has found many uses in maths and sciences:

• in astronomy: the brightest star in a constellation. For instance, Betelgeuse is designated as α Orionis
• in biochemistry: α-helix, a type of protein secondary structure
• in inorganic chemistry: a symbol for certain (usually the most common) allotropes, for example α-iron, α-phosphorus, and α-sulphur
• in natural product chemistry: a stereodescriptor used in a number of different ways
• in navigation: a symbol for azimuth
• in neurophysiology: α-waves, a type of brain waves detected by electroencephalography
• in nuclear physics: alpha particle, α or α²⁺, a historical name of doubly ionised helium nuclei (He²⁺) ; α-decay is a radioactive process in which an atomic nucleus emits an α-particle
• in organic chemistry: the α-carbon is the first carbon atom attached to a functional group; α-amino acids are amino acids with an amino group bound directly to the α-carbon
• in pharmacology: α₁ and α₂, subtypes of adrenergic receptors
• in physics: a symbol for angular acceleration
• in physics: the fine-structure constant
• in zoology: α-males and α-females, the highest ranking individuals in a community of social animals

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白 | bái

In Mandarin Chinese, 白 (Pinyin: bái 🔊) means “white”, “clear”, “pure”, “bright” and a number of other meanings which at some point probably were related to colour white: “spoken language”, “free of charge”, “in vain” or “funeral”.

Does it look and sound familiar? This is because we’ve already came across 百 (bǎi), “hundred”. You may also recall that the shape of 百 is a combination of 一 and 白.

While 白 looks like a modification of 日, “sun” or “day”, Uncle Hanzi links 白 with the moon. However, Wiktionary says its original meaning was “acorn”:

The character acquired its current meaning of white from the color of the acorn’s flesh. The original meaning has been lost.

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好 | hǎo | hào

In Mandarin Chinese, 好 (Pinyin: hǎo 🔊) means “good”, “well”, “nice”, “easy” and so on. This character also has another, slightly different pronunciation (hào 🔊) meaning “to like” or “to be easy to”.

I’m sure you’ve noticed that 好 is made up of two familiar characters, 女 and 子. But why? According to Wiktionary,

The widely accepted meaning of this character is that the characters for “female” (女) and “child” (子) were put together to form a compound because it was good for a woman to have a child. Similarly, it has been proposed that the compound originally refers to the mutual affection between the mother and child, which then extended to mean “good”. These theories are supported by the smaller 子 found in some oracle bones and bronze inscriptions.

However, broader interpretations of the second character 子 could lead to other theories. 子 could also mean “son”, so it may have meant two children, a boy and a girl next to each other, which is a good fortune to have a boy and a girl. 子 could also mean “man”, so it may have referred to the love between a man and a woman, which is good. Duan Yucai, in his annotated version of Shuowen, interpreted it as originally referring to the beauty of 女子 (nǚzǐ, “woman”). Lastly, it could mean that the “attitude” of a girl was considered good.

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子 | zǐ

In Mandarin Chinese, 子 (Pinyin: zǐ 🔊) has many meanings. As a noun, it can signify “a child”, “an offspring”, “a son”, “a person”, “a seed” or “an egg”, while as an adjective, it means “young” or “small”.

子 is also the first of twelve earthly branches. It corresponds to the Year of the Rat (鼠) of the Chinese zodiac; the eleventh month; the hour of the Rat (11 pm to 1 am, “the time when Rats are most active in seeking food”); and the direction 0° (i.e. north). Its associated “fixed element” is Water, 水.

Curiously, a combination of 男 “man” with 子, 男子 (nánzǐ), still means “a man”, not “a boy” as one would expect; similarly, 女 + 子 = 女子 (nǚzǐ) means “a woman”, not “a girl”. (This is not the case in Japanese where 男子 and 女子 mean exactly that: “a boy” and “a girl”, respectively.) However, an anagram of 女子, 子女 (zǐnǚ), means “children”, i.e. “sons and daughters”.

Many historical forms of 子 show a baby with a large head and spread arms (the legs are presumably swaddled). To remember the pronunciation of this word, I think of it as a variant of Latin letter Ƶ (pronounced American way, /ziː/ 🔊).

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