Any decent dictionary (I use the Shorter Oxford English, in the main) will tell you that ‘binomial’ (mod. L. binomium) is a term in mathematics (actually, two terms!) whereas ‘binominal’ (fr. L. binominis) indicates two names. OK, it was first confused in 1656 - but I find the persistent universal use of the former for taxonomy as a tiresome abbreviation. Is it laziness? Does anyone have a good argument in favour? Am I just a pedant?!
binomen (pl. binomina), n., or binominal name.
The combination of two names, the first being a generic name and the second a specific name, that together constitute the scientific name of a species [Art. 5.1]. Any interpolated names [Art. 6] are not counted as components of a binomen.binominal nomenclature
See under nomenclature.Binominal Nomenclature, Principle of
See Principle of Binominal Nomenclature.
from International Code for Zoological Nomenclature. And thanks, I hadn’t noticed that significant N before.
Got me! I’ve apparently been using the term “binomial” in error for decades.
Binomial is well-established in reference to biological nomenclature even if the Code suggests otherwise. I’m all for getting rid of extra letters in words when they don’t add anything.
Maybe it depends on what you consider a “decent dictionary”? Or maybe it’s an American vs. British English thing. Merriam-Webster’s [app on my iPhone, not the book] does not even include binominal and defines binomial thus:
1 : a mathematical expression consisting of two terms connected by a plus sign or minus sign
2 : a biological species name consisting of two terms
The American Heritage English Dictionary [iPhone app] likewise does not include binominal and defines binomial thus:
[Adjective] Consisting of or relating to two names or terms.
[Noun] 1 : Mathematics - A polynomial with two terms. 2 : Biology - A taxonomic name in binomial nomenclature.
I have been taught binomial, and this is the term used in textbooks. I don’t think it’s reasonable to call it an error. Googling shows plenty of sources use “binomial” (e.g. Wikipedia, which also mentions binominal). Maybe its origin was erroneous usage, but at this point it has passed into common language usage. Kind of like one of my personal pet peeves, the rise in the past decade of the use of “decimated” to mean “wiped out”…sigh…
And don’t get me started about “nonplussed.” But I digress.
I prefer nominate subspecies to nominotypical subspecies simply because it’s easier to say and write.
Language is like a taxon; it adapts to its environment. It is a living thing that is never static! Grammar purists might want to freeze it in amber, but you can’t fight change; you can only adapt to it. All of us on the forum have adapted to a new way of surveying biodiversity: using iNaturalist. Let’s embrace language change as well!
@jnstuart: “I’m all for getting rid of extra letters in words when they don’t add anything.”
Me to.
Perhaps it would only irritate someone whose interests start with mathematics (or Planet B for zoology ;~)), then turned to biology. Use of binomiNal spiked in the fifties … then dwindled away.
Binomial is the preferred usage
And for those of us who live on Planet Botany not Planet B – there is NO extra N in the Code.
binary combination (binomial). A generic name combined with a specific epithet to form a species name
This botanist was trained up from the beginning with binomial (and trinomial).
Quite so! I’ve long since given up on “data is,” “specie,” “taxons,” etc., in everyday communication. Though if reviewing a manuscript for publication, I will still “correct” them to data are, species, taxa, etc. Soon there will be no one left who sees anything to correct in those constructions.
And that’s a major reason why in the binomial (or binominal, for anyone who prefers) naming system, the actual words chosen as names are frequently based on ‘dead’ languages; to try and minimise the chances of their meanings changing over time.
‘binomial’ and ‘binominal’ have roughly the same etymology, as afar as I am aware. If I wanted to be really pedantic, I would criticise the phrase ‘binomial name’ (or ‘binominal name’) as tautologous :)
Scientific Esperanto to bridge our about 7K human living (and now dead) languages.
Roughly 44% of all languages are now endangered, often with fewer than 1,000 users remaining. Meanwhile, the world’s 20 largest languages are the native tongue of more than 3.7 billion people total. That’s just 0.3% of the world’s languages accounting for nearly half of the world’s population!
from https://www.ethnologue.com/insights/how-many-languages/
It’s perhaps better to compare “binomial nomenclature” with “binominal nomenclature”, since “binomial” and “binominal” have other uses outside of biology (especially the former in mathematics):
But of course, this still strongly suggests that “binomial” has almost always been much more popular in biology, and now seems completely dominant.
By themselves, the words obviously have a much longer history (i.e. pre-dating Linnaeus’ Species Plantarum and Systema Naturae), but the overall picture is much the same:
So it seems that “binominal” is just a tiresome aberration favoured by pedants 
I majored in maths.
It is easier to overload the meaning of ‘binomial’ than to remember and use an extra word for no benefit.
Anyway, binominal has the same rhythm as manamana and gives me an earworm.
I had not realized they were sometimes spelt the same. I learned BinoMIAL as taxons, and BinoMINAL as the mathematics.
That being said, I had an increasingly strange education, homeschooled till college. Now I hold a B.S. and I’d love to go back and finish my biology/ecology degree but I don’t want to have to take calculus. Its the bane of my existance.
The International Code for Zoological Nomenclature or whoever endorsed it does not have the authority to redefine common terms.
It seems like they lack the linguistic nous and an ear for connotations as well.
nomen (adj nomial) name, binomial is the correct Latin term
nominal - signals face value, title without power or substance, insignificance
binominal - a cringe inducing word of dubious meaning. Wikipedia describes it in italic as “not a typographic error”
No wonder usage has dropped off.
It’s amusing to find that “binomial” isn’t mentioned at all in their glossary - not even as an alternative spelling! And their main site search just gives: “Sorry - no matches found for ‘binomial’”.
It seems that the ICZN is the only one of the various nomenclatural codes to insist on “binominal”. I didn’t check them all, but the ICNafp only includes “binomial” in their glossary, and the ICNP also only appears to use that term.
Perhaps “binomial” has become a shibboleth for those inside the ICZN 
Good to see you using ‘pre-dated’, as do I, instead of the ambiguous ‘predated’, Barry.