Rhotacism and How It Can Help Your Latin

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If you have studied a little Latin, you may have come across an important, yet rather annoying group of nouns. They belong to the third declension, are neuter in gender and end in -us in the nominative singular. They include words like tempus ‘time’, corpus ‘body’ and pectus ‘chest’.

They look like nice second-declension nouns, like masculine dominus and amīcus, but the trouble begins when you look at their various declined forms. Let’s take corpus as the group’s representative.

	Singular	Plural
Nominative	corpus	corpora
Genitive	corporis	corporum
Dative	corporī	corporibus
Accusative	corpus	corpora
Vocative	corpus	corpora
Ablative	corpore	corporibus

With the exception of the nominative, vocative and accusative singular, the -us of corpus ending disappears and -or- appears, seemingly out of nowhere, bringing with it an awful headache for Latin students.

I tell my students to remember whether or not a noun belongs to this group by thinking of an English word that descends from it. For example, tempus, corpus and pectus gave English the adjectives temporal, corporal and pectoral, which reveals the -us/-or- change.

However, we want to do better than tricks like this; we want to understand this phenomenon. This article aims to show you how one linguistic idea, rhotacism, can explain these words.

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Neuter? No ending!

The first step is to try to identify what the actual case-number endings of these twelve forms could be — that is, to separate the constant from the inconstant parts of the word, which have nothing to do with its ‘body’ meaning, but rather its function in the sentence. By comparing corpus with other nouns of the same gender and declension, these are the case-number endings that we can identify:

	Singular	Plural
Nominative	corpus	corpor – a
Genitive	corpor – is	corpor – um
Dative	corpor – ī	corpor – ibus
Accusative	corpus	corpor – a
Vocative	corpus	corpor – a
Ablative	corpor – e	corpor – ibus

The suffixes we have separated from the rest of the word are exactly the same case-number endings used by other third-declension neuter nouns, such as caput ‘head’ or nōmen ‘name’. Let’s follow that similarity and take a closer look at nōmen.

	Singular	Plural
Nominative	nōmen	nōmina (nōmin – a)
Genitive	nōminis (nōmin – is)	nōminum (nōmin – um)
Dative	nōminī (nōmin – ī)	nōminibus (nōmin – ibus)
Accusative	nōmen	nōmina (nōmin – a)
Vocative	nōmen	nōmina (nōmin – a)
Ablative	nōmine (nōmin – e)	nōminibus (nōmin – ibus)

Nōmen reveals something important. We can see that the case-number suffixes we have identified are simply added to the nominative/accusative/vocative singular form, with only a small change to its second vowel. The N/A/V singular form itself has no suffix; instead, it is both a stem and a complete, stand-alone word.

Being also a third-declension neuter noun, we should apply this analysis to the corpus group of words. When we do, we see that the -us on the end of corpus is not a case-number suffix. It is instead an inseparable part of the word’s stem, to which the real endings can be added. We can therefore call corpus and company ‘s-stems’, and this brings them into line with other neuter nouns of the third and fourth declensions, such as caput or cornū, in that nothing is added to form their nominative/accusative/vocative singular forms.

This idea is corroborated by a sound change that took place in Old Latin: -us on the end of words like both corpus and dominus was originally -os. The older form of corpus therefore was *corpos, which has the same -o- vowel as the one we see in the corpor- forms.

We can therefore deconstruct corpus into the following system of twelve forms:

	Singular	Plural
Nominative	corpos	corpos – a
Genitive	corpos – is	corpos – um
Dative	corpos – ī	corpos – ibus
Accusative	corpos	corpos – a
Vocative	corpos	corpos – a
Ablative	corpos – e	corpos – ibus

However, one crucial step remains. How do we get from words like *corposa and *corposibus, which we have reconstructed, to their actual documented forms corpora and corporibus? We can do so in a single step: the sound change known as rhotacism.

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So, what is rhotacism?

Its name taken from the Greek letter rho, rhotacism is the change of a particular sound into a rhotic sound like [r], the sound known in English as a rolled or trilled R. Many sounds can become [r] over time, but a common candidate is [z] (as in zoo), since both are pronounced with the tip of the tongue and are voiced.

When the case-number suffixes were first added to *corpos, the process of rhotacism began. This is the key to rhotacism. It was through being sandwiched between two vowels that the /s/ in *corposa and *corposibus became voiced [z]. This brought the consonant one step to /r/ and, in time, potentially though other intermediate stages, rhotacism occurred and produced the -or- forms of corpus, tempus and pectus as we know them.

So, in brief:

Intervocalic /s/ became /r/ in Classical Latin

This was a very early change in the history of Latin, but we do in fact have a few examples of Old Latin that display the original /s/ prior to rhotacism. For instance, the text of the Praeneste fibula (seventh century BC) and the Lapis Satricanus (sixth/fifth century BC) attest the names Numasioi and Valesiosio. These would become Numeriō and Valeriī by the time of Classical Latin.

Meanwhile, the -os at the end of the N/A/V singular forms of corpos and the rest would become classical -us in an unrelated development, unaffected by any endings or rhotacism.

To sum up, we have the following stages:

Structure	Stage 1	Stage 2	Classical result
*corpos	*corpos	*corpos	corpus
*corpos + a	*corposa	*corpoza	corpora
*corpos + ibus	*corposibus	*corpozibus	corporibus

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Seeing rhotacism in practice

It was not only this group of nouns that rhotacism affected; it had a language-wide effect, and we can find traces of it everywhere.

It explains the English adjectives already mentioned, corporal, pectoral and temporal. These were formed in Latin through the addition of the suffix -ālis. Since -ālis begins with a vowel, it triggered rhotacism on the final consonant of the original noun. Hence *corposālis and *temposālis became corporālis and temporālis.

Let’s look at the nouns ōs ‘mouth’, flōs ‘flower’ and mūs ‘mouse’. They have a different appearance to corpus, and mūs and flōs are also masculine in gender, not neuter. Once again, when the relevant case-number endings were added to these words, in nearly all cases the final /s/ of the stem found itself hemmed in between two vowels and the change into /r/ began. For example, the addition of the genitive singular suffix -is resulted in the genitive forms ōris, flōris and mūris.

	Singular	Plural
Nominative/Vocative	–s > flōs, mūs	–ēs > flōrēs, mūrēs
Genitive	–is > flōris, mūris	–um > flōrum, mūrium
Dative	–ī > flōrī, mūrī	–ibus > flōribus, mūribus
Accusative	–em > flōrem, mūrem	–ēs > flōrēs, mūrēs
Ablative	–e > flōre, mūre	–ibus > flōribus, mūribus

Moreover, the addition of the same adjective ending -ālis involves the same change. This is how the Latin nouns ōs and flōs have given English oral and floral. Latin also derived a verb of the first declension from ōs: ōrāre, meaning ‘to plead, pray’. From this come English orate and adore.

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Esse, the Latin verb for ‘to be’, is a tricky verb to learn. It is very irregular. However, it is also important in any language, and doubly so in Latin, because its various forms also provide the endings for some tenses. For example, eram not only means ‘I was’, but it’s also used as a verb ending, as in vīderam ‘I had seen’. It definitely needs learning, and rhotacism can help with this task.

We should first recognise that the present stem of the word is es-. It is from es- that the verb gets its meaning of ‘to be’, and we can see the stem in the infinitive esse and the present tense forms est ‘it is’ and es ‘you are’. Like other verbs in the present tense, es and est are formed with the addition of the simple endings -s and -t (specifically es-s and es-t). Yet in other tenses, the endings that are added to es- start with vowels, such as -am, -ās, -at for the imperfect and –ō, -is, -it for the future. These, having sandwiched the /s/ between two vowels, cause rhotacism. Thus *esam, *esat and *esis become eram, erat, eris, etc.

Present stem	Ending and its meaning	Result
es- +	-s Second-person singular present indicative	es
es- +	-t Third-person singular present indicative	est
es- +	–āmus First-person plural imperfect indicative	erāmus
es- +	–unt Third-person plural future indicative	erunt
es- +	-se Present infinitive	esse

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Rhotacism is also responsible for the -re that defines present infinitives. The ‘original’ ending for the infinitive was -se, but it changed when attached to the present stem and its final vowel sound. The rhotacised ending can be seen in the vast majority of infinitives like amāre ‘to love’, monēre ‘to warn’ and venīre ‘to come’, from older *amāse, *monēse and *venīse The original -se has survived in a handful of verbs whose present stems end in consonants, such as esse ‘to be’ and nōsse ‘to know’.

We can also observe rhotacism below the level of whole words. We are taught that there are six genitive plural endings, –ārum, -ōrum, –um, –ium, –uum and -ērum, but we can do better than this. The ‘real’ genitive plural suffix is what unites them, -um, while what remains originates elsewhere. Since the vowel in -um was able to cause the rhotacism of the preceding consonant, we can deconstruct –ārum, -ōrum and -ērum as the results of –ās-um, -ōs-um and -ēs-um. The three affixes that emerge, –ās-, -ōs– and -ēs-, are identical to the accusative plural endings of their respective declensions, and fairly similar to the genitive singular endings –ās and -is.

On this matter at least, I do not want to suggest any ideas for the reasons behind this system (I am aware it likely emerged in pronouns rather than in nouns) or for the precise nature of –ās-, –ōs– and –ēs-; it’s just for another example of the explanatory power of rhotacism.

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To conclude

In sum, rhotacism is a sound change that transforms a given consonant in a language into a rhotic consonant like [r]. It has been hugely important for the development of Latin as we know it. Most significant is the change from intervocalic /s/ to /r/, traces of which are still visible in many words, and which is a source of apparent irregularity — yet rhotacism is a very regular change, and recognising its effects is one way to dispel a lot of confusion.

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Featured image from here.