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Origin Adapted from Phoenician consonantal script, about the 8th century BCE
Kappa is the tenth letter of the Greek alphabet, from the Phoenician kaph, meaning palm of the hand, and the ancestor of Latin K. It sounds the k, and its value in isopsephy is twenty, placing it twentieth in the numeral order. In statistics Cohen's kappa measures inter-rater agreement; in physics kappa denotes curvature, thermal conductivity, and the dielectric constant; in physiology a kappa is a class of opioid receptor.
Facts
Origins
Origin PeriodAdapted from Phoenician consonantal script, about the 8th century BCE 1Tradition: The Greek alphabet and the Milesian numerals Origin PeriodEvery European alphabet descends from that decision 1Tradition: The Greek alphabet and the Milesian numerals Origin PeriodInnovation: wrote vowels with letters of their own 1Tradition: The Greek alphabet and the Milesian numerals Place of OriginPrecise place disputed: Al Mina, Cyprus, Crete, Euboea all argued for 1Tradition: The Greek alphabet and the Milesian numerals Place of OriginThe Aegean world, at a point of contact with Phoenician traders 1Tradition: The Greek alphabet and the Milesian numerals Origin of the NameAlpha, beta, gamma are aleph, bet, gimel: ox, house, camel 1Tradition: The Greek alphabet and the Milesian numerals Origin of the NameClearest evidence the alphabet was taken over, not invented 1Tradition: The Greek alphabet and the Milesian numerals Origin of the NameGreek letter names are borrowed Semitic words meaning nothing in Greek 1Tradition: The Greek alphabet and the Milesian numerals Sense of the Namepalm of the hand (from Phoenician kaph) 1Tradition: The Greek alphabet and the Milesian numerals The pictographic sense is a modern reconstruction from the letter name rather than a meaning attested in the script's own period, and the atlas records that position elsewhere on this letter. The name itself is inherited; the picture behind it is inferred. Attestation
Meaning in the Attesting SourceIsopsephy (Greek gematria) attested in inscriptions and magical papyri 1Tradition: The Greek alphabet and the Milesian numerals Meaning in the Attesting SourceThe 27-sign series used three lost letters: digamma/stigma, koppa, sampi 1Tradition: The Greek alphabet and the Milesian numerals Meaning in the Attesting SourceThis atlas's 24 letters hold none of those three 1Tradition: The Greek alphabet and the Milesian numerals Identity
Script TypeAn alphabet: each letter writes a single sound, consonant or vowel, inherited from Phoenician's twenty-two consonantal signs but repurposing several of them, for the first time in the alphabet's history, to write vowels outright. 1 PositionTenth of twenty-four in the Greek alphabet 1 Attributions
Associated Sound Learn More
Kappa: The Greek Letter (Value 20), From Palm of the Hand
Kappa is the tenth Greek letter, from Phoenician kaph ('palm of the hand'); its value is 20. Kappa has no significant independent esoteric tradition; its interest is linguistic and, through isopsephy, numerical. The Greek letters doubled as numerals in the Milesian (alphabetic) system, in which each letter carried a fixed value; the practice of summing a word's letters into a number, called isopsephy, is the Greek counterpart of Hebrew gematria and appears in inscriptions, the Greek Magical Papyri and early Christian texts. Kappa's Phoenician ancestry places it in a borrowing whose exact point of contact, somewhere among Al Mina, Cyprus, Crete and Euboea in the Aegean world, is still disputed, though the borrowing itself, conventionally dated to around the 8th century BCE, is agreed to be the ancestor of every European alphabet still in use, including the Latin one covered elsewhere in this atlas.
The Greeks' own contribution was to give vowels dedicated letters of their own, something the consonant-only Phoenician script never did. Its isopsephy value of 20 belongs to the Milesian alphabetic numeral system, which also needed three further, otherwise obsolete letters, digamma (also called stigma), koppa and sampi, to cover every value from 1 up to 900; none of the three survives among the 24 letters in ordinary use today.
Kappa in Modern Use
Kappa carries a scattered set of modern technical meanings, none connected to the letter's ancient Semitic root kaph, meaning the palm of the hand, discussed elsewhere in this atlas. Physicists use kappa for a variety of constants depending on context, including the spring constant in Hooke's law and measures of curvature in geometry and general relativity; statisticians use Cohen's kappa, introduced by the psychologist Jacob Cohen in 1960, as a standard measure of agreement between two independent raters that corrects for the agreement expected by pure chance, a tool still widely used in fields from medicine to content moderation research.
Kappa is also, unusually among Greek letters, one of the more graphically stable across the alphabet's history, its angular shape essentially unchanged from the Phoenician kaph it descends from, since, unlike letters such as beta or sigma, its ancient consonant value never shifted or split into rival forms. Astronomers, following the Bayer star-naming convention of 1603, use Kappa to mark a constellation's eleventh- or twelfth-brightest star, continuing the sequence used for the alphabet's other letters. In the Milesian numeral system, discussed elsewhere in this atlas, kappa holds the value twenty, a role with no bearing on any of its later scientific or statistical uses.
Cross-Tradition Connections
Derived from This
The Latin letter K descends from Greek Kappa, reaching Latin through the Etruscan adaptation of a Western Greek alphabet. Latin kept K only in a few fossilised spellings once C had taken over the sound.
Why this is disputed. Glagolitic Kako is read as Greek Kappa's counterpart in an alphabet Cyril modeled on Greek order and numeral values, but which theory explains where its rounded letterform actually came from is a live paleographic dispute. The mainstream palaeographic school, developed since Isaac Taylor's nineteenth century study, derives Glagolitic's ornamental shapes from medieval Greek cursive minuscule redesigned for Slavonic use. A rival idiographic school reads Glagolitic as substantially an original invention, its shapes built from basic forms such as the cross, circle and triangle rather than borrowed from any existing script, so this specific correspondence to Kappa is accepted by one camp and denied by the other.
Kako takes its shape from Greek kappa and its numeral value of 20 from the same letter.
Taken over into heavy native use, since Egyptian had a k of its own
Related To
Roman K and Greek Kappa continue the same Phoenician kaph.
Samaritan Kaaf and Greek Kappa both continue the same Phoenician sign, and both write k.
Greek Kappa and Hebrew Kaph are cognates. Both continue the same Phoenician sign, which is why both carry the numeral value 20 in their letter-number systems. A shared ancestor, not a borrowing in either direction. The Greek alphabet was adapted from the Phoenician abjad in the early first millennium BC, and the Hebrew square script descends from the same abjad through Aramaic.
Hebrew Kaph and Greek Kappa continue the same Phoenician kaph; both carry the numeral value 20 in their letter-number systems.
Coptic Kappa is the Greek kappa, a k sound Egyptian already had of its own; both carry the numeral value 20.
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