How to say (pronounce) $\partial$ in the context of homology?

Question

I am curious what is the common way to say (in English contexts) the name of $\partial$ (the boundary homomorphism) in homology theory. I.e. when giving a talk / speaking.

The boundary homomorphism is $\partial: C_n\to C_{n-1}$ when $(C_\bullet, \partial_\bullet)$ is a chain complex.

Some possibilities I can think of is:

• "Boundary"?
• "Del"?
• "Partial"?
• "Dee"? (it looks like a letter $d$)
• "Delta"?

Thanks for any insights.

I haven't found any answer online despite some searching. How do you pronounce (partial) derivatives? is similar in a sense (same symbol $\partial$) but the context is entirely different.

Answer 1

In my experience there is no single standard pronunciation, though "del" is probably the most common. I have heard all of the possibilities you suggest except "delta" used. If you want to maximize the chance that you will be understood, I would recommend just saying "(the) boundary of" rather than trying to pronounce it as a single word. In cases where you really want a shorter pronunciation, I think "del" is probably the best choice, but as Mike Miller commented the most important thing is to be consistent and unambiguous.