Here comes the third piece in our series of articles on the Greek alphabet letters: we are examining the Theta symbol today. Here is you need the know about the Theta letter, its meanings and uses in science, math and other fields across the world.

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**Theta – Origins and Symbolisms**

Theta, written in ancient Greek as θῆτα and as θήτα in modern Greek has an uppercase (Θ or ϴ) and lowercase (θ) symbol. Both resemble the number 0 or a circle or oval with a horizontal line in the middle. It is the eighth letter of the Greek alphabet, and is known to have been derived from the Phoenician letter Teth. In the Greek numeral system, Theta has a value of 9.

In Ancient Greek, Theta represented the aspirated voiceless dental plosive /t̪ʰ/. Meanwhile, in modern Greek, it represents the voiceless dental fricative /θ/.

The Cyrillic letter Fita is said to have been derived from the Greek’s Theta.

In ancient times, Theta was used to symbolize death, while Tau (another Greek letter) represented life and resurrection. True enough, in ancient Athens, the Theta sign was used as an abbreviation for thanatos (θάνατος), which means death. This is because the symbols somewhat resemble a skull.

**Theta – Uses in Different Fields in the Modern Times**

Aside from the symbolism that Theta was associated with during the ancient times, there are many other ways the Greek symbol is still being used today. Because Theta has a different symbol for upper and lowercase, and the symbols are not similar to any letters of the Latin or English alphabet, they both have different uses in the fields of math, science, and other fields.

**Uses for the Uppercase Theta Symbol**

The uppercase Theta letter Θ or ϴ has various uses in the modern world. For instance, it is used to denote the dimension of temperature, as specified by the SI standard (International System of Units). It also represents the dimensionless temperature in transport phenomena, a field of study in engineering, chemistry, and physics.

The uppercase Theta also represents the asymptotically tight bound in the analysis of algorithms in computer science. This refers to the “big O notation”.

In set theory, the uppercase Theta sign denotes a certain ordinal number. Meanwhile, in particle physics, it symbolizes the exotic baryons, Pentaquarks.

In neurology, Theta signifies a brain signal frequency that ranges from 4-8 Hz. It is joined by Beta, Alpha, and Delta.

Theta also signifies the variable that indicates temperature difference when it comes to heat transfer. The symbol also denotes the angle of incident X-ray beam in X-ray scattering techniques.

In finance, Theta is considered one of the variables that represent time decay of options.

**Uses for the Lowercase Theta Symbol**

The lowercase Theta letter θ also has various uses when it comes to representing different values, measurements, and other aspects.

One of its primary uses is representing a plane angle in geometry. It also denotes an unknown variable in trigonometry. Meanwhile, it symbolizes the special function of a series of complex variables.

In prime number theory, the lowercase Theta signifies one of the Chebyshev functions. Meanwhile, in meteorology, it is used to denote potential temperature.

The term “Theta” is used in Theta Type Replication. This is a type of DNA replication of bacteria, specific to circular chromosomes.

In neurology, the lowercase Theta represents the threshold value of artificial neuron.

As the eighth letter of the Greek alphabet, the Theta was used to symbolize the Bayer designation. This refers to the eights star in a constellation as seen from the Earth.

The lowercase Theta letter also represents the statistical parameter commonly used to write the likelihood function. In the study of population genetics, Theta sign represents the Watterson estimator for the population mutation rate.

In economics, the lowercase Theta denotes the reserve ratio of banks. It also has a use in pharmacology, where it represents the fraction of ligand bound to a macromolecule, as denoted by the Hill Equation.

The lowercase Theta also signifies the Heaviside step function, also known as the unit step function. It also represents the ordinal collapsing function, a technique developed by Solomon Feferman.

**How to Type the Theta Symbol**

Do you need to type or insert the Theta symbol on a document or spreadsheet? Fortunately, there are several ways to do so.

**How to Type Theta Symbol in Word**

If you’re creating a report or article and you need the Theta symbols added to your Word document, there are several techniques you can use.

First, you can use the Insert tab, then go to Equations. Click on the arrow or dropdown, then look for the Theta sign you need.

Another way is to use the Insert tab again, but this time use the Symbol option. When you click on Symbol, the dialog will open. In the field “Subset:” choose Greek and Coptic. In the field “from:” choose Unicode (hex). Then, look for the Theta symbol. Select it, then click Insert. Close the dialog window.

If you have a numerical keypad on your keyboard, you can also use an Alt code. Press and hold the Alt key, then press the code 952.

**How to Insert Theta Symbol in Excel**

If you need to insert the Theta symbol in an Excel cell, you can also use the Insert function. Just like with inserting it on a Word document, you can go straight to Insert > Symbol. Then, change the required fields as described above, then choose the Theta sign you need to insert into your sheet.

Moreover, you can also look for the symbols online, copy them, and paste on your Excel document.

**How to Type Theta Symbol on Mac**

It’s very easy to add the Theta symbol when using a Mac computer. You can use a very simple keyboard shortcut. Simply press the Option key, and while holding it, press G, then Q or J.

This concludes our piece on the Theta symbol. If you liked reading it, you will surely enjoy reding about other Greek alphabet letters. Simply, check them out through the main menu please. Thanks for reading!