# What is the pronounciation of this letter in english?

## Main Question or Discussion Point

Hello
My native language is not English an i have a noob! question about the pronounciation of the derivative operator letter in English and how we write its name in English, i have attached the picture of operator.
Thanks

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CompuChip
Homework Helper
It's called "del" or "partial", although in "colloquial" usage people often say "d" when they mean "del".

HallsofIvy
Homework Helper
First, it is not a "letter" in the English alphabet. It is a special symbol. I, myself, have never heard it called "del". To me "del" is the vector operator, "nabla", $\nabla$. If f(x, y, z) is a real valued function of x, y, and z (Cartesian coordinates) then "del f" (also called "grad f") is the vector function
$$\nabla f= \frac{\partial f}{\partial x}\vec{i}+ \frac{\partial f}{\partial y}\vec{j}+ \frac{\partial f}{\partial z}\vec{k}$$
Similarly, I have heard "div v" called "del dot v" and "curl v" called "del cross v" for vector function v, though I would not consider any of those as formal as "grad", "div", or "curl".

I have, though, heard $\partial$ called "curly d". The LaTex code for it is "\partial".

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tiny-tim
Homework Helper
Hello gholamghar! Yes, ∂ isn't an English letter or even a Greek letter like ∑ or π, it's just a symbol.

I believe a lot of people pronounce it "dabba", but I just pronounce it "d" (though I call it "curly d"). (and I also have never heard it pronounced "del", that's for ∇)

Redbelly98
Staff Emeritus
Homework Helper
I generally say "partial of f with respect to x", if I want to talk about ∂f/∂x. The symbol "∂" never appears by itself, so I have never worried about what to call it.

CompuChip
Homework Helper
I, myself, have never heard it called "del". To me "del" is the vector operator, "nabla", $\nabla$.
Whoops, you are so right.
I meant to say "dau" ([dow]).
* deeply ashamed *

∂ is a letter of Cyrillic alphabet, right? I remember my teacher said it in a lesson.
$$\frac{\partial f}{\partial x}$$
as "de" f over "de" x

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Several of my lecturers pronounce it "del." Others use "del" to refer to the gradient operator, as has been mentioned, which can be confusing. Ways I have heard it pronounced from educated people:

Del,
Dau,
D,
Partial.

Mark44
Mentor
∂ is a letter of Cyrillic alphabet, right?
Sort of. In Russian, the cursive form of lower case Д is sometimes written as ∂, and sometimes as g. That's always been a little confusing to me. This wike article, http://en.wikipedia.org/wiki/Cyrillic_alphabet, has some good information.
I remember my teacher said it in a lesson.
$$\frac{\partial f}{\partial x}$$
as "de" f over "de" x

To my knowledge, we say "partial". That's what I've always heard and was told a while ago.

Mark44
Mentor
∂ is a letter of Cyrillic alphabet, right? I remember my teacher said it in a lesson.
$$\frac{\partial f}{\partial x}$$
as "de" f over "de" x
If you say "dee" f over "dee" x, someone listening would likely interpret this as the ordinary derivative instead of a partial derivative. There have been a number of times where I was helping someone with calculus over the phone. In such cases you have to be more clear than when you can see the work.
To my knowledge, we say "partial". That's what I've always heard and was told a while ago.
Yeah, me, too. I always pronounce this as "partial of f with respect to x."

If you say "dee" f over "dee" x, someone listening would likely interpret this as the ordinary derivative instead of a partial derivative. There have been a number of times where I was helping someone with calculus over the phone. In such cases you have to be more clear than when you can see the work.
Yes you're right. Here, we use the name of $$\partial$$, that is dɛ in IPA.

Nabeshin
$$\partial_x = \frac{\partial}{\partial x}$$