Between Twenty and Twenty-One: Synchrony and Diachrony — Two Ways of Understanding Language

Introduction

Why do some English numerals, such as sixteen, seventeen, eighteen and nineteen, clearly display their internal composition (six + teen), while others — eleven and twelve — do not reveal such structure? At first glance, this may appear to be a trivial irregularity. Yet the contrast conceals a profound theoretical question: how can a single linguistic system contain signs that expose their internal logic while others conceal it?

The answer depends on the perspective from which we observe language. From a historical or diachronic point of view, the focus falls on the origin and evolution of forms. From a synchronic perspective, by contrast, the interest lies in their present functioning, regardless of their past.

In the first case, the linguist reconstructs genealogies; in the second, the speaker simply uses the signs as they exist in the current system. This distinction between studying the history of language and studying its present structure lies at the heart of the methodological revolution proposed by Ferdinand de Saussure.

The Diachronic View: Genealogy of Forms

From a diachronic perspective, the irregularities among English numerals are legacies of the language’s Germanic past. Words such as eleven and twelve derive from Old English endleofan and twelf, themselves based on Proto-Germanic forms meaning roughly “one left (after ten)” and “two left (after ten).” Over time, these expressions contracted and lost their internal transparency.

By contrast, sixteen, seventeen, eighteen, and nineteen are later and more transparent compounds, built on the productive model number + teen (where teen derives from ten). They reflect a process of regularization that tends toward greater formal clarity. From this point of view, irregular forms are residues of an earlier stage of the language, while regular forms mark a systematizing tendency. The historical linguist, therefore, seeks evolutionary causes: older and more frequent words tend to fossilize early and preserve their opacity.

Yet the ordinary speaker does not think about Old English or about the phonetic changes that shaped the language. They live in the present of their linguistic system, where twelve and seventeen exist as current signs with distinct values.
This shift in focus — from origin to structure — marks the passage from historical to synchronic analysis.

The Copernican Turn: Saussure and Synchrony

Ferdinand de Saussure revolutionized linguistics by arguing that language should be studied in its current state, as a system of interdependent relations. In the Course in General Linguistics, he distinguished two complementary modes of analysis:

• Diachrony, which studies changes over time, and
• Synchrony, which examines the relations among coexisting elements at a given moment.

The contemporary English speaker does not possess the memory of Old English, but rather the structural competence that organizes their present language. Therefore, the difference between twelve and sixteen cannot be explained by history alone, but by their function within today’s linguistic system.

Within this framework, sixteen is analyzable: it is composed syntagmatically of six and teen, and connects with other forms following the same pattern (seventeen, eighteen, nineteen, twenty-six, six thousand).

Twelve, on the other hand, behaves as an indivisible unit, without recognizable internal parts in the contemporary system. The difference between the two is not one of origin, but of structure.

Relative Motivation: The Internal Order of the System

Saussure calls this phenomenon relative motivation: although all linguistic signs are arbitrary in origin, some display an internal coherence that allows their composition to be recognized. He writes:

“The fundamental principle of the arbitrary nature of the linguistic sign does not prevent us from distinguishing in any language between what is intrinsically arbitrary – that is, unmotivated – and what is only relatively arbitrary. Not all signs are absolutely arbitrary. In some cases, there are factors which allow us to recognise different degrees of arbitrariness, although never to discard the notion entirely. The sign may be motivated to a certain extent. The French word vingt (‘twenty’) is unmotivated, whereas dix-neuf (‘nineteen’) is not unmotivated to the same extent. For dix-neuf evokes the words of which it is composed, dix (‘ten’) and neuf (‘nine’), and those of the same numerical series: dix (‘ten’), neuf (‘nine’), vingt-neuf (‘twenty-nine’), dix huit (‘eighteen’), soixante-dix (‘seventy’), etc. Taken individually, dix and neuf are on the same footing as vingt, but dix-neuf is an example of relative motivation.”
(Saussure, Course in General Linguistics, trans. Roy Harris, 2013, ch. VI)

The essential point here is that Saussure does not refer to the past or to external motivation — he is not invoking resemblance between sound and thing, as in onomatopoeia, a notion he rejected. Rather, the motivation he describes is internal: it arises from the structural relations within the linguistic system itself. Twenty-one refers to twenty and one, but these terms are internal to the code, not to the world.

Thus, twenty functions as an arbitrary sign — it cannot be decomposed into meaningful parts — whereas twenty-one participate in a network of syntagmatic and associative relations that grant it partial motivation. In this way, Saussure nuances his famous principle of arbitrariness: language is not a chaotic collection of conventions, but a structured system in which internal relations constrain arbitrariness and stabilize meaning.

Within the English numeral system, the forms eleven and twelve stand as opaque, unmotivated signs, while sixteen to nineteen represent relatively transparent combinations. A speaker need not know historical etymology to perceive this difference; it suffices to grasp the oppositions and associations that constitute their linguistic competence.

Conclusion

The comparison between twelve and sixteen reveals two ways of understanding language.
For the historical linguist, the irregularity is a vestige of the evolution of Old English.
For Saussure, it is instead a synchronic difference in the degree of internal motivation among signs.

What may seem a mere numerical curiosity thus becomes a fundamental lesson about the nature of language: language is not a collection of words with histories, but an autonomous system of differential values, in which each sign signifies only through its position within the total network.

That network, while grounded in arbitrariness, also regulates it: it establishes points of anchorage that make signification possible — or, in Lacanian terms, provides a point de capiton against the infinite drift of the signifier.

References

• Saussure, Ferdinand de. Course in General Linguistics. Trans. and annotated by Roy Harris. Bloomsbury, 2013.
• Harris, Roy. Reading Saussure. London: Duckworth, 1987.
• Joseph, John E. Saussure. Oxford: Oxford University Press, 2012.