What is Reddit's opinion of A Maths Dictionary for Kids CD-ROM: Mult-e-Maths UK?
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If a site uses the term "maths", it's probably not American: We spell "math" without an "s".

In particular, both of those first two links are British (and the second one incorrectly calls it a synonym for "variable"); the first one doesn't make it obvious, but a search for its author led to this clearly British book.

Anyway, I did check The Free Dictionary, another meta-dictionary of sorts, and it redirects from "pronumeral" to "variable": http://www.thefreedictionary.com/Pronumeral

I was about to remark on the distinction between different localized Google sites after trying google.com.au on my feature-phone, but I just tried it in Google US and it showed the same relevant results.

In conclusion, "pronumeral" really needs to spread around the Anglosphere: I believe that students will be less confused if they have one single word for the symbol and a different single word for the changeable quantity that it represents.

I just did a small part by adding it to Wiktionary and even finding a proper citation for it in a review guide for Grade 9 maths.

P.S.: You probably have access to the Macquarie Dictionary at your local or university library; I wonder whether "pronumeral" is at least in that dictionary, or maybe in the Australian Oxford, which is also not available online (illicitly or otherwise) and also rather expensive to obtain for a foreigner (a third of the price of the Macquarie but still).