In a previous post, we shared a brief description of each of the Greek alphabet letters, including Theta. In today’s article, we are having a more detailed discussion of the Greek symbol. So, without further ado, here’s everything you should know about Theta, the eighth letter of the Greek alphabet, its many meanings and various uses.

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## Greek Theta Symbol Meaning, Symbolism and Origin

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, the Theta letter 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 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 symbol was used as an abbreviation for Thanatos (θάνατος), which means death. This is because the symbols somewhat resemble a skull.

## How to Use Greek Theta Sign in Math and Science

Aside from the symbolism that the Theta sign was associated with during ancient times, there are many other ways the Greek symbol is still being used today.

Because the Theta letter 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 Letter

The uppercase Theta sign 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 symbol 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 the incident X-ray beam in X-ray scattering techniques.

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

### Uses for the Lowercase Theta Symbol

The lowercase Theta sign 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 an artificial neuron.

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

The lowercase Theta also represents the statistical parameter commonly used to write the likelihood function. In the study of population genetics, Theta 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 letter 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 sign while 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 wraps up our piece on the Greek Theta symbol, its meaning and various uses in math and science. If you enjoyed reading it, please check out our other pieces on the Lambda symbol here and the Pi symbol here. See you in the next post.