Θ

Zeta (according to the RAE since 2001) or theta (in capital letters Θ, lowercase θ [italics ϑ]; call in ancient Greek θῆτα < i>thêta /tʰɛ̂ː.ta/, in modern Greek θήτα thíta /ˈθi.ta/) is the eighth letter of the Greek alphabet. Its pronunciation in ancient Greek was that of an aspirated t (AFI [tʰ]), which the Romans transliterated as "th" in words of Greek origin such as theatrum, thalamus, thermae and Thales (words that later passed into Spanish as theater, thalamus, thermal baths, Thales). In modern Greek it represents a voiceless dental fricative [θ], like the z of non-sounding Spanish, for example μυζήθρα is transcribed as mizithra although it is pronounced approximately "midsizra" #3. 4;.

Until its 1992 dictionary, the Royal Spanish Academy called theta θ and zeta to ζ; in the 2001 edition, as zeta (Θ, θ) and dseta (Ζ, ζ), which were maintained in later publications. It was also called teta in ancient works such as in the Treasure of the Castilian or Spanish language by Sebastián de Covarrubias of 1611.

In the Greek numeral system it has a value of 9 (Θ΄).

History

In its archaic form, θ was written as a cross within a circle (as in the Etruscan or ) and later, as a line or a point within a circle (or). Signs that remember the cross archaic forms of theta can be seen in the letters in the wheel shape of Linear A and Linear B.

In Latin writing used for the galo language, theta inspired tau gallicum (). It is believed that the phonetic value of tau gallicum Could have been [t supporting].

Epigraphic variants

In archaic epigraphic sources the following variants appear:

Use

In ancient Greek, θ represented the voiceless aspirated dental plosive /t̪ʰ/, but in modern Greek represents the voiceless dental fricative /θ/.

Cyrillic

The Cyrillic letter fita (Ѳ, ѳ) was developed from the Greek theta. This letter existed in the Russian alphabet until the Russian spelling reform of 1918, which eliminated it because its sound had merged with that of ef (Ф). An example of this is the name of the Crimean city of Feodosia (Феодосия) which was founded by Greeks with the name Theodosia (Θεοδοσία).

International Phonetic Alphabet

In the International Phonetic Alphabet (IPA), [θ] represents the voiceless dental fricative, as in the Spanish of Spain zapato or the English thin. It should not be confused with the consonant in English th e, which is a voiced dental fricative. A similar-looking symbol, [ɵ], described as a barred lowercase O, indicates in IPA a closed-mid rounded central vowel.

Symbolism

Old

In ancient times, tau was used as a symbol of life or resurrection, while the eighth letter of the Greek alphabet, theta, was considered the symbol of death.

According to Porphyry of Tyre, the Egyptians used an X within a circle as a symbol of the soul; which having a value of nine, was used as a symbol of the Ennead. Juan Lido says that the Egyptians used a symbol for the Cosmos in the form of theta, with a circle of fire representing the world, and a serpent in the middle representing the Agathos Daimon (literally: good spirit).

The Egyptians also used the symbol of a point within a circle (, the solar disk) to represent the sun, which could be a possible source of its use as astrological glyph of the Sun. It is worth noting that θ margin (theta) has the same numerical value in isosefy as Ηλιος (Helios): 318.

Abbreviation

In classical Athens, it was used as an abbreviation of the Greek θάνατος (thanatos, "death"). One possibility that may have played a role is how it vaguely resembles a skull, in the same way that the skull and crossbones are used in modern times. It survives in the ostracs used by the Athenians when voting for the death penalty. Petrus of Dacia, in a document from 1291, relates the idea that theta was used to brand criminals with fire as empty figures (0), and that the marking mast was fastened to the cross bar that crossed the circle. For this reason, the use of the theta number was sometimes avoided when the connotation was considered unfortunate: the mint marks of some coins of the Roman Empire late have the famous sum ΔΕ or ΕΔ (delta and epsilon, that is, 4 and 5), a euphemism where a theta (9) would be expected.

Science

The lowercase letter θ is used as a symbol:

• In mathematics and sometimes in physics it usually represents an angle.
• In phonetics it serves for the transcription of a consonant sound, fricative, dental, deaf; like that of Spanish (not sessing) "zapatoθä.'pä.to.].

The capital letter Θ is used as a symbol:

• In statistics to represent a seasonal average mobile model, MA(Q).
• In computing to express the asymptotic set in complexity of algorithm analysis.

Unicode

The italic form ϑ appears in Unicode as U+03D1, different from the lowercase theta U+03B8 θ. For the purpose of writing Greek text, the two can be single-character font variants, but θ and ϑ are also used as distinct symbols in technical and mathematical contexts.

• Greek

• Copt

• Cyrillic

• Maths