For Greek loanwords in Latin and modern languages with Latin alphabets, psi is usually transliterated as "ps".
The letter's origin is uncertain. It may or may not derive from thePhoenician alphabet. It appears in the 7th century BC, expressing/ps/ in the Eastern alphabets, but/kʰ/ in theWestern alphabets (the sound expressed byΧ in the Eastern alphabets). In writing, the early letter appears in an angular shape ().There were early graphical variants that omitted the stem ("chickenfoot-shaped psi" as: or).[citation needed]
The Western letter (expressing/kʰ/, later/x/) was adopted into theOld Italic alphabets, and its shape is also continued into theAlgiz rune <ᛉ> of theElder Futhark.
Psi, or its Arcadian variant or was adopted in the Latin alphabet in the form of "Antisigma" (Ↄ, ↃC, or 𐌟) during the reign ofEmperor Claudius as one of the threeClaudian letters.[2] However, it was abandoned after his death.[citation needed]
U+1D7A7𝞧MATHEMATICAL SANS-SERIF BOLD ITALIC CAPITAL PSI
U+1D7C1𝟁MATHEMATICAL SANS-SERIF BOLD ITALIC SMALL PSI
^TheMATHEMATICAL characters are used in math. Stylized Greek text should be encoded using the normal Greek letters, with markup and formatting to indicate text style.
^Weisstein, Eric W."Polygamma Function".mathworld.wolfram.com. Retrieved2025-02-08.A special function mostly commonly denoted ψ_n(z), ψ^((n))(z), or F_n(z-1)...
^"About - The Parapsychological Association".www.parapsych.org. Retrieved2025-02-09.The Parapsychological Association, Inc. (PA) is the international professional organization of scientists and scholars engaged in the study of 'psi' (or 'psychic') experiences, such as telepathy, clairvoyance, remote viewing, psychokinesis, psychic healing, and precognition.
^IUPAC-IUB Commission on Biochemical Nomenclature (1970). "Abbreviations and symbols for nucleic acids, polynucleotides, and their constituents".Biochemistry.9 (20):4022–4027.doi:10.1021/bi00822a023.
^"Torsion Angles and the Ramachnadran Plot in Protein Structures".proteinstructures.com. Retrieved2025-02-09.These angles describe the rotations of the polypeptide backbone around the bonds between N-Cα (called Phi, φ) and Cα-C (called Psi, ψ) and essentially determine the fold of the protein.
^Although the university itself refers to its logo as atrident, not the Greek letter psi:"The IU trident—the only logo at Indiana University". Indiana University. Retrieved2020-07-31.At IU, the trident is the only logo we use, both institution-wide and at the unit level.
^Rein, Alan (2020-07-28)."The heart of the HIV RNA packaging signal?".Proceedings of the National Academy of Sciences of the United States of America.117 (33).doi:10.1073/pna (inactive 18 July 2025).PMC7443930.vRNA is selectively packaged because it contains a "packaging signal" or "ψ" [also designated the "core encapsidation signal" (2)].{{cite journal}}: CS1 maint: DOI inactive as of July 2025 (link)
^Srivastava, Manishi; Varma, Vishwanath; Abhilash, Lakshman; Sharma, Vijay Kumar; Sheeba, Vasu (June 2019). "Circadian Clock Properties and Their Relationships as a Function of Free-Running Period in Drosophila melanogaster".Journal of Biological Rhythms.34 (3):231–248.doi:10.1177/0748730419837767.ISSN1552-4531.PMID30939971.... 2) accuracy (i.e., day-to-day stability of the phase relationship (ψ), where ψ is the duration between a phase of the rhythm and a phase of the external cycle) is greater for clocks with τ close to 24 h; ...
