In the second part of our series about the Greek letters, we willl take a closer look at the Delta symbol, the fourth letter of the Greek alphabet, its meaning, origins and uses throughout history.

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**Delta Sign – Summary and Origins**

Delta (uppercase Δ, lowercase δ or 𝛿; written in Greek as δέλτα), is the fourth letter of the ancient Greek alphabet. In the Greek numeral system, Delta holds the value of 4.

As with other Greek letters, Delta is believed to have also been derived from a Phoenician letter. It is related to the Phoenician letter, dalet. Meanwhile, the Latin letter D is essentially derived from Delta. The Cyrillic letter Д is also considered to be a variation of the Greek letter Δ.

In Ancient Greek language, the letter Delta represented a voiced dental plosive /d/. Meanwhile, in Modern Greek phonetics, it represents a voiced dental fricative /ð/, similar to the “th” in “this” or “that”. Delta is also romanized as d or dh.

**Delta Symbol – Meanings and Uses in Different Fields**

You are probably already familiar with “Delta” as a term. Indeed, the Delta letter is used as both a symbol and a term for several things.

For instance, a river delta is called as such because of its triangular shape, which is similar to the uppercase delta letter. It’s good to note that this term, contrary to the popular legend, was not coined by Herodotus.

Delta sign also stands for the letter D in the NATO phonetic spelling military alphabet. Delta is joined by other another Greek letter, Alpha, in the NATO spelling alphabet. Alpha stands for the letter A.

Aside from these more popular use for Delta as a term, there’s a wide range of other uses for both the upper and lowercase Delta symbol.

**Uses for the Uppercase Delta (Δ)**

There are various uses for the uppercase Delta symbol in the fields of science and mathematics.

Delta represents the change of any changeable quantity. As such, it symbolizes the difference operator in science and math equations. The triangle-like uppercase Delta is also used to symbolize the Laplace operator. It also represents the discriminant in a polynomial equation, particularly a quadratic equation.

Because the uppercase Delta symbol is essentially a triangle, it is also used to denote the area of a triangle. It also represents the symmetric difference between two sets of elements. Uppercase Delta is also used to denote a macroscopic change, as well as the uncertainty in a physical variable, as related to the uncertainty principle.

In physics, the uppercase Delta symbolizes delta particles. Meanwhile, in chemistry, it represents the addition of heat in a particular reaction.

The symbol is also used in legal shorthand, where it represents “defendant”. In music, it is the major seventh chord in jazz notation.

Furthermore, the American Dental Association considers the uppercase Delta symbol, together with Omicron, as the symbol of dentistry.

**Uses for the Lowercase Delta (δ or 𝛿)**

There are also a lot of uses for the lowercase Delta letter. In calculus, it denotes the value of a variable, as well as a functional derivative in functional calculus. Another way it is used in calculus is to define the continuity or limit of a given function.

Other uses for the lowercase Delta in mathematics include representing the Kronecker delta, the degree of vertex in graph theory, and the Dirac delta function.

Meanwhile, it is used to denote deflection in engineering mechanics, as well as the force of interest in actuarial science.

In chemistry, the lowercase data is used to denote the chemical shift of nuclear magnetic resonance. It also represents the relative electronegativity of the different atoms in a particular molecule. It also represents partial charge.

The lowercase Delta symbol is also used in astronomy to denote the declination of an object in an equatorial coordinate system. Meanwhile, in macroeconomics, it represents the rate of depreciation of an aggregate capital stock of a particular economy.

In electricity, the Delta sign denotes the angle between current and voltage in a system that shows electrical reactance.

**How to Type the Delta Symbol**

Because of the so many uses for both the upper and lowercase symbol, you may find the need to type it at one point or another. It can be tricky to add the symbols onto your documents, but there are definitely ways to do it.

**How to Type the Delta Symbol in Word**

There are several ways to type or insert the Delta symbol in a Word document.

One method is to use an Alt code. The Alt code for Delta sign is 0394. To use this, place the insertion pointer where you need to add the symbol. Then, type the Alt code 0394. Next, press Alt+X. The code will automatically transform into a Delta symbol.

Meanwhile, you can also use the Insert Symbol Dialog. In your Word document, click on the Insert tab, then look for the Symbol tab. You may need to choose “More Symbols…”. On the Symbol dialog, you can type in the “Character code” box the code 0394. Then on the “from:” dropbox, choose “Unicode (hex)”. You can also specify “Greek and Coptic” on the “Subset:” dropdown. Look for the Delta sign you need, then click Insert.

**How to Insert a Delta Symbol in Excel**

Inserting symbols in Excel is a bit complicated than typing them in Word. Fortunately, there are several workarounds.

You can use a keyboard shortcut to insert a solid triangle to represent the uppercase Delta letter. To do this, select the cell where you need to insert the symbol. Then, press F2 to enter edit mode. Use the shortcut by pressing Alt + 30. Note, however, that this will only work if you have the numeric keypad.

A fast way to insert Delta sign into your Excel file is to simply copy it from another source and paste it on your sheet. You may also use the Insert Symbol dialog, the steps of which are the same as when you insert in a Word document (refer above).

**How to Type Delta Symbol on Mac**

It’s quite easier to type the Delta symbol on a Mac, particularly on MS Word installed in a Mac. Simply press Option + J and voila! You’ve got the Delta symbol on your doc. If this doesn’t work, a simple copy-and-paste may do the trick.

Did you enjoy reading about the Delta symbol? Then, you might want to check out our other posts on the Greek alphabet through the sections in the top menu. Thanks for reading!