Endings

First of all, let’s have a look at endings, also known as inflectional suffixes. In highly inflected languages such as Latin or Russian endings change depending on number, gender and case. In Russian, there are three noun declensions:

Case	feminine (I)		neuter (II)		masculine (II)		feminine (III)
	singular	plural	singular	plural	singular	plural	singular	plural
Nominative	кислота	кислоты	основание	основания	спирт	спирты	соль	соли
Genitive	кислоты	кислот	основания	оснований	спирта	спиртов	соли	солей
Dative	кислоте	кислотам	основанию	основаниям	спирту	спиртам	соли	солям
Accusative	кислоту	кислоты	основание	основания	спирт	спирты	соль	соли
Instrumental	кислотой	кислотами	основанием	основаниями	спиртом	спиртами	солью	солями
Prepositional	кислоте	кислотах	основании	основаниях	спирте	спиртах	соли	солях
	acid	acids	base	bases	alcohol	alcohols	salt	salts

Adjectives have to agree with the nouns for number, gender and case, with corresponding change in endings.

Case	feminine, singular		neuter, singular		masculine, singular
Nominative	хлористая	ртуть	хлористое	железо	хлористый	натрий
Genitive	хлористой	ртути	хлористого	железа	хлористого	натрия
Dative	хлористой	ртути	хлористому	железу	хлористому	натрию
Accusative	хлористую	ртуть	хлористое	железо	хлористый	натрий
Instrumental	хлористой	ртутью	хлористым	железом	хлористым	натрием
Prepositional	хлористой	ртути	хлористом	железе	хлористом	натрии
	Hg2Cl2		FeCl2		NaCl

Apart from marking the plural, the different endings do not change the meaning of the word or phrase. Ask any Russian chemist, or non-chemist.

In languages that lack cases, e.g. in Spanish, endings still depend on gender and number, and adjectives have to agree with the nouns in both gender and number:

number / gender	feminine		masculine
singular	molécula	orgánica	compuesto	orgánico
plural	moléculas	orgánicas	compuestos	orgánicos
	organic molecule(s)		organic compound(s)

Contrast that with modern English which has very few endings, and the only endings for nouns are the plural markers ‘-s’ (regular plurals) and ‘-en’ (irregular)^*.

What’s your point, you may ask. Patience, I’m getting to it.

In a number of IUPAC publications, the entities that are referred to as “endings” include

• ‘en’, ‘ese’, ‘ic’, ‘ide’, ‘ine’, ‘ium’, ‘ogen’, ‘on’, ‘orus’, ‘um’, ‘ur’, ‘y’, ‘ygen’ in element names [1];
• ‘ane’, ‘ene’, ‘yne’ in hydrocarbons [2];
• ‘-yl’, ‘-ylidene’, ‘-diyl’ in derivatives of cyclic parent hydrides [3];
• ‘-ose’, ‘-onic acid’, ‘-onate’, ‘-onamide’, ‘-ononitrile’, ‘-onolactone’ in carbohydrates [4];
• ‘-liberin’, ‘-tropin’, ‘-statin’ [5];
• ‘-conta-’,‘-cta-’ and ‘-kis-’ as parts of “multiplying prefixes” [6];
• parent compounds [7, p. 5].

Well my point is that very few of these “endings” are endings from the natural language point of view. And comparison with corresponding terms in other languages helps to make it clear. For example, the respective Spanish terms for benzene and somatostatin are benceno (masculine) and somatostatina (feminine). Note that ‘-en-’ and ‘-statin-’ are still there but the real endings are ‘-o’ and ‘-a’, respectively.

English	Latin	French	German	Russian	Spanish
lithium	lithium	lithium	Lithium	литий	litio
platinum	platīnum	platine	Platin	платина	platino
phosphorus	phōsphorus	phosphore	Phosphor	фосфор	fósforo
boron †	bōrium	bore	Bor	бор	boro
neon †	neon	néon	Neon	неон	neón
bromine	brōmium	brome	Brom	бром	bromo
chlorine	chlorum	chlore	Chlor	хлор	cloro
manganese	manganum	manganèse	Mangan	марганец	manganeso
pentane	pentanum	pentane	Pentan	пентан	pentano
butene	butenum	butène	Buten	бутен	buteno
propyne	propinum	propyne	Propin	пропин	propino
phenyl	phenyl	phényle	Phenyl	фенил	fenilo
glucose	glucosum	glucose	Glucose	глюкоза	glucosa
gluconate	gluconatum	gluconate	Gluconat	глюконат	gluconato
somatotropin	somatotropinum	somatotropine	Somatotropin	соматотропин	somatotropina

Most chemical element names end in ‘-um’ which is just a copy of Latin nominative ending ‘-um’ as in lithium, platīnum, etc. So ‘-um’ looks like a genuine, albeit imported, ending. Ditto ‘-us’ in “phosphorus”. On the other hand, ‘-ine’ in halogen names is rather a suffix. The word “chlorine” was coined by Sir Humphry Davy from the Ancient Greek root χλωρ- (“pale green”) and ‘-ine’, an English suffix derived from Latin suffix ‘-īnus’, used to form adjectives out of nouns (cf. “canine”, “piscine”, “porcine” etc.). The rest of halogens acquired ‘-ine’ by analogy with chlorine.

According to Wikipedia, “the origin of the name manganese is complex” but as it came in the current form from Italian, I’d imagine ‘-ese’ is a suffix+ending (the corresponding plural form is ‘-esi’; cf. milanese, milanesi). As for ‘-on’ in “boron” — named by the same Humphry Davy, apparently by analogy with carbon, itself derived from French carbone — it probably is an ending^†. No other language wants it anyway.

The other “endings” mentioned above are even less qualified to be called “endings”: their semantic content is too high. Some of them are suffixes, some are roots. I hope to go into more details in future blog posts. In the meantime, I allow myself to hypothesise that at least some of English terminal ‘e’s are in fact endings. Because their analogues in other languages, e.g. Latin ‘-um’, Russian ‘-а’, Spanish ‘-o’ or ‘-a’ are nothing but endings.

What about plural ‘-s’? It is a proper ending and, on top of that, with non-zero semantic load. So it can be, and is being, employed in chemical nomenclature to differentiate between a substance and classes of substances: cf. phenol and phenols, porphyrin and porphyrins, urea and ureas and so on.

*	Cf. Old English which had five cases and adjectives agreeing with the nouns for number, gender and case.
†	The ending ‘-on’ in carbon, silicon and boron should not to be confused with ‘-on’ of noble gases. The name “neon” was derived from the Ancient Greek word νέον, where ‘νέ’ is a root and ‘ον’ is a neuter singular ending. In Latin, neon inflects as a neuter second-declension noun: neon, neī, neō etc., i.e. ‘ne’ is a root, just like in Greek. In many other inflected languages, however, ‘neon’ behaves as a root. Other noble gases, apart from helium, were named by analogy with neon.

References

1. Hartshorn, R.M., Hellwich, K.-H., Yerin, A., Damhus, T. and Hutton, A.T. (2015) Brief guide to the nomenclature of inorganic chemistry (IUPAC technical report). Pure and Applied Chemistry 87, 1039—1049.
2. Hellwich, K.-H., Hartshorn, R.M., Yerin, A., Damhus, T. and Hutton, A.T. (2020) Brief guide to the nomenclature of organic chemistry (IUPAC technical report). Pure and Applied Chemistry 92, 527—539.
3. Powell, W.H. (1988) Nomenclature for cyclic organic compounds with contiguous formal double bonds (the δ-convention) (Recommendations 1988). Pure and Applied Chemistry 60, 1395—1401.
4. McNaught, A.D. (1996) Nomenclature of carbohydrates (IUPAC recommendations 1996). Pure and Applied Chemistry 68, 1919—2008. 2-2-Carb-20. Aldonic acids.
5. IUPAC‐IUB Commission on Biochemical Nomenclature (CBN). The nomenclature of peptide hormones. Recommendations, 1974.
6. Lozac’h, N. (1986) Extension of Rules A-1.1 and A-2.5 concerning numerical terms used in organic chemical nomenclature (Recommendations 1986). Pure and Applied Chemistry 58, 1693—1696.
7. Connelly, N.G., Hartshorn R.M., Damhus, T. and Hutton, A.T. Nomenclature of Inorganic Chemistry: IUPAC Recommendations 2005. Royal Society of Chemistry, Cambridge, 2005.