Modern print theta, in a typical uppercase and two different lowercase glyph forms.
In itsarchaic form, θ was written as a cross within a circle (as in the Etruscan or), and later, as a line or point in circle ( or).
In modern print, lowercase theta may appear in two different forms: one resembling the uppercase form, like a zero with a horizontal bar through it, and one more cursive style featuring an open loop, resembling a nine. For use as a mathematical symbol, where the difference between the two forms may be significant, a dedicated Unicode symbolU+03D1ϑGREEK THETA SYMBOL was introduced, which always displays the open-loop form. There is alsoU+03F4ϴGREEK CAPITAL THETA SYMBOL, which differs from most realizations of the normal textual uppercase letter by having a cross-bar that goes all the way across, touching the outer O-shape on both sides.
In the Latin script used for theGaulish language, theta inspired thetau gallicum (Ꟈ ꟈ). The phonetic value of thetau gallicum is thought to have been[t͡s].[1] In addition, multiple modern languages written in Latin script useLatin theta.
ABayer designation letter applied to a star in a constellation; usually the eighth star so labelled but not necessarily the eighth-brightest as viewed from Earth[9]
Indicates a minimum optimum integration level determined by the intersection of GG and LL schedules (The GG-LL schedules are tools used in analyzing the potential benefits of a country pegging their domestic currency to a foreign currency.)[12]
One of the variables known as"Greeks" in finance, representing time decay of options or the change in the intrinsic value of an option divided by the number of days until the option expires[20]
In ancient times,Tau was used as a symbol forlife orresurrection, whereas the eighth letter of the Greek alphabet (ninth in the archaic form anciently used for numeration), theta, was considered the symbol ofdeath.[21] A quotation attributed to the ancient Roman authorEnnius (though possibly spuriously) said of it: "oh, theta, a letter much unluckier than the others".[22]
According toPorphyry of Tyros, theEgyptians used an X within a circle as asymbol of the soul; having a value of nine, it was used as a symbol forEnnead.Johannes Lydus says that theEgyptians used a symbol forKosmos in the form of theta, with a fiery circle representing the world, and a snake spanning the middle representingAgathos Daimon (literally:good spirit).[23]
In classical Athens, it was used as an abbreviation for theGreek θάνατος (Thanatos, "death") and as it vaguely resembles a human skull,[23] theta was used as a warning symbol ofdeath, in the same way thatskull and crossbones are used in modern times.[23] It survives onpotsherds used by Athenians when voting for thedeath penalty.[23]Petrus de Dacia in a document from 1291 relates the idea that theta was used to brand criminals as empty ciphers, and the branding rod was affixed to the crossbar spanning the circle.[24] For this reason, the use of the number 9 was sometimes avoided where the connotation was felt to be unlucky—the mint marks of some Late Imperial Roman coins famously have the sum ΔΕ or ΕΔ (delta and epsilon, that is 4 and 5) substituted as aeuphemism where a Θ (9) would otherwise be expected.
^TheMATHEMATICAL characters are used only in math. Stylized Greek text should be encoded using normal Greek letters, with markup and formatting to indicate text style.
^International Phonetic Association (2021).Handbook of the International Phonetic Association: a guide to the use of the international phonetic alphabet (22. printing ed.). Cambridge: Cambridge University Press. p. 177.ISBN978-0-521-63751-0.θ Theta voiceless dental fricative
^Weisstein, Eric W."Angle".mathworld.wolfram.com. Retrieved2025-02-01.
^Holton, James R.; Hakim, Gregory J. (2013).An introduction to dynamic meteorology (Fifth ed.). Amsterdam: Academic Press. p. 87.ISBN978-0-12-384866-6.Since potential temperature θ is conserved following the motion in adiabatic flow, a parcel of air which movees adiabatically will remain on the same potential temperature surface.
^Ahsan, Amimul, ed. (2011).Convection and Conduction Heat Transfer. Erscheinungsort nicht ermittelbar: IntechOpen. p. 57.ISBN978-953-307-582-2.θ dimensionless temperature,...
^van der Linden, Wim J.; Hambleton, Ronald K. (2018).Handbook of Item Response Theory, Three Volume Set. Chapman & Hall / CRC Statistics in the Social and Behavioral Sciences (1st ed.). Boca Raton: CRC Press. pp. section 10.2.ISBN978-1-4665-1439-3.θp is test taker p's factor score or latent trait parameter.
^Bakich, Michael E. (1995).The Cambridge guide to the constellations. Cambridge: Cambridge University Press. p. 109.ISBN978-0-521-46520-5.To designate the 24 brightest stars in the constellation, Johannes Bayer used the lowercase letters of the Greek alphabet:
^Casella, George; Berger, Roger W. (2024).Statistical inference. CRC texts in statistical science series (Second ed.). Boca Raton: CRC Press. p. 8.ISBN978-1-032-59303-6.Likelihood is the most directly accessible inferential element for estimation statements about θ conditional on f...
^Hösel, Volker (2020).Mathematical population genetics and evolution of bacterial cooperation. New Jersey: World Scientific. p. 75.ISBN978-981-12-0549-1.
^Reszat, Beate (2005).European financial systems in the global economy. Chichester, West Sussex, England ; Hoboken, NJ: Wiley. pp. 223–224.ISBN978-0-470-87056-3.As a consequence, the critical level for joining shifts from θ to θ' -...
^Damill, Mario; Rapetti, Martín; Rozenwurcel, Guillermo, eds. (2016).Macroeconomics and development: Roberto Frenkel and the economics of Latin America. Initiative for policy dialogue. New York: Columbia University Press.ISBN978-0-231-17508-1....θ and θ* are reserve ratios in DC and FC...
^Ali Elkordy, Amal, ed. (2013).Applications of Calorimetry in a Wide Context: Differential Scanning Calorimetry, Isothermal Titration Calorimetry and Microcalorimetry. Erscheinungsort nicht ermittelbar: IntechOpen. p. 75.ISBN978-953-51-0947-1.Saturation fraction, θ. The fraction of the total number of sites of the macromolecule occupied by ligand molecules.
^Singh, Balwant; Arbestain, Marta Camps; Lehmann, Johannes, eds. (2017).Biochar: a guide to analytical methods. Clayton South: CSIRO Publishing. p. 246.ISBN978-1-4987-6553-4.θ is the angle between the incident x-ray beam and the diffracting plane
^Lemons, Don S. (2017).A student's guide to dimensional analysis. New York: Cambridge University Press. p. 50.ISBN978-1-107-16115-3.The physics of heat transfer requires two dimensions, temperature Θ and heat H, beyond those that characterize non-equilibrium dynamics.
^Ursone, Pierino (2015).How to Calculate Options Prices and Their Greeks: Exploring the Black Scholes Model from Delta to Vega. The Wiley Finance Series (1st ed.). Newark: John Wiley & Sons, Incorporated. p. 2.ISBN978-1-119-01162-0.Θ (time decay): the price change of an option in relation to time;
