Phonetic evolution: why and how does the pronunciation of a language change over time?

What causes changes to occur in the pronunciation of languages, and how do these changes function exactly?

This article was translated by Nayan Velaskar. Thanks, man! <3 (Please credit him too if you share this!)

Phonetic evolution is what causes regional accents. When this applies to a bigger context -one having as much to do with space as to do with time- we see these accents as the reason Romance languages (which all derived from Latin) have evolved to the point where their pronunciation became completely different.

A language passes through many evolutions at a given time, the foremost of which being phonetic, lexical and morphological. While all these changes are incidents which occur on the pronunciation of a language, I will address here only the direct influence of phonetic changes.

  Doing so excludes, for example, the possibility of grammatical assimilation (changes in certain paradigms -such as conjugations- through the imitation of other structures; those are an indirect cause of phonetic changes, such as the S which appears from the Latin ”dīcō” to the French ”dis”) or the possibility of etymology (barbarisms, idiotisms, neologisms… ). 


Family tree of Indo-European and Uralic languages ⓒ Minna Sundberg

To begin with…

Would you believe me if I said that the sound /r/ (the Spanish trill) can become the vowel /a/? This is conceivable… under certain conditions.

First of all, we will need to set in place time and spatial criteria:

  • phonetic changes are an extremely slow process, particularly in the modern world, to the point where it’s difficult to notice them in a single lifespan;
  • phonetic changes do not occur in an entire language at a time; yet, they occur all over. For example, a phonetic change could affect:
    • an idiolect (fig. 1 given below)
    • a dialect (fig. 2 given below)
    • a language (fig. 3 given below)

Phonetic changes (for example from Latin to French) can be listed and are consistent (even though subject to condition, meaning that there can be exceptions, but these exceptions can be listed and their existence is explainable), and gradually spread -or don’t spread- in a manner that is justifiable and coherent. A phonetic change applies to all the words of a language at a time, therefore explaining their consistency. There certainly exist some irregularities and exceptions, but these happen to be fairly marginal. 

  • A phonetic change could be fixed in an idiolect (that is to say, one single person makes use of it and it will not spread beyond the scope of said user)…
  • …or become a dialect (that is to say that it propagates just enough to become a particularity of a regional accent)…
  • …or continue to spread (or become standardized) within a whole language, such that it changes the standard and subsequently participates in the divergence of the language in relation to its cousins.

Paying heed to the examples illustrated above, the two primary phonetic changes take place within languages but the third is the result of the adaptation of a language towards many others. These variations can be demonstrated simply via illustration, such as the evolution of the Latin /i/ to the French /wa/, which had beenprogressive and conditional; an evolution resulting from favorable conditions and time.  

The reference I made to standardization above was to stress how standardization acts as a real ”boost” to phonetic changes. While Old French in the Middle Ages was a group of dialects close to one another, the French we hear today comes from a specific dialect: the Francien, the Parisien dialect standardized by the Ordinance of Villers-Cotterêt in 1539. The same occurred in modern English, caused however by the natural standardization of Anglo-Norman (that is to say, through propagation, and not due to a law imposed) during the invasion of Normandy in 1066 (thus 60% of English vocabulary is Romance, stemming from this dialect).


There is a notion that I want to convey above all through this article : that the phonetic evolution of a language isn’t random, difficult though it may be to believe from the outset. It is globally regular and is often governed by a collection of verifiable rules. Phonetic changes are often subject to conditions, and these conditions result largely in divergences and convergences seen in the phonological elements of a language; and by overlapping one another, such convergences and divergences tinge phonetic changes with an aspect of unpredictability. Yet this unpredictability is an illusion.

The standardization of a language could have pretty much the same consequences.

We’re lucky to be speaking French (this might be the case if one was reading the original article, but everyone is welcome!). I say this because French has ”cousins” which aren’t all too distant, Portuguese, Spanish, Italian and Romanian amongst others. They’re sufficiently distant enough to let us reflect upon the common points between them, so as to question specifically: how did Latin diverge so much that it resulted in Romance languages? While this is an abstract question, we have some fairly concrete answers to it. We also have the fortune to know what Latin looked like, given the immense store of the language that was conserved, through which we’re able to answer this question to a large degree.

As I was saying, phonetic changes are expressed by a collection of rules which are globally consistent. We are also able to write down these rules, the syntax of which is as follows:

x → y / z

x = target replaced ; y = target replacement ; z = given condition

Of course, z is optional but as seen subsequently, conditions are quite influential in phonetic changes. As we can expect from this, a change di → d͡ʒ signifies simply that ”/di/ is replaced by /d͡ʒ/ ” (for example : lat. ”hodiē” → ita. ”oggi”).

While the purpose of this article is not to enter into the details of such linguistic language programming, certain elements of the syntax are still necessary in order to illustrate evolution from Latin. Notably, the capital letters that form categories; by convention, V signifies ”any vowel” and C ”any consonant”, but nothing stops us from determining other categories such as N={m,n,ŋ} (we can thus imagine the category N signifying ”any nasal consonant”). Another important element is the underscore: _ , which is always equal to x.

Then, we can write the following phonetic change:

di → d͡ʒ / _V

Which expresses ”/di/ is replaced by /d͡ʒ/ if /di/ is placed before a vowel”. The part which I have underlined is referred to as an ”environment”.

It would be tedious to get into the details of real phonetic changes, therefore I’m simply going to conclude this chapter by a fictive (but plausible) example. Let’s consider the following phonetic changes:

di → d͡ʒ / _V

di → zi

These mean ”/di/ is replaced by /d͡ʒ/ if /di/ is placed before a vowel, and replaced by /zi/ everywhere else”. In my fictive example derived from Latin, we can therefore observe the following evolutions:

/ho.dieː/ → /ho.d͡ʒeː/

/diː.koː/ → /ziː.koː/

It’s necessary to consider other parameters so that this phonetic change could occur, which I’ve needed to disregard in order to simplify the example. Notably, these parameters are:

  • the length of the vowels (represented by /ː/);
  • lexical stress;
  • as it is, my example doesn’t give room to exception, which isn’t altogether thorough (considering for example the most frequent words are often irregular since they erode much faster);
  • Please note as well that I have only made use of the phonetic change for /di/ on these words, but it would be quite possible to employ others!

As expected, the given example presents the divergence from /di/, in Latin, towards two different possibilities depending on the environment, which (fictively) stated in the same language are: /zi/ and /d͡ʒ/. Sometimes these divergences end up distinguishing different languages. 

Sometimes we observe convergences, such as the fusion of the sounds /ĩ/ and /ɛ̃/ of Old French, which come together to form /ɛ̃/ in modern French (being the reason the sound /ɛ̃/ can be represented notably by ”in” as in ”fin”, or by ”en” as in ”bien”).

Due to this set of rules often being consistent, phonetic changes from one language to another form a continuum that can be span into the past (which permitted certain reconstructions like Proto-Indo-European, based on the use of comparative linguistics) and into the future (giving us an idea of what future languages may look like).

We know what Romance languages look like, and we know what Latin looked like. Phonetic changes between the two are thus evident. Before Latin, we had no realistic conception of the progenitor of Romance and Indo-European Languages… barring a possible comparison between all Indo-European languages (comparative linguistics based on our knowledge) allowing us to conceive a common and probable origin. Since lack of precise date makes it impossible to trace seven millennia into the past without error, this blind guess is the best we have.

There exist some rare phonetic changes referred to as ”sporadic”, therefore random changes. Let’s consider ”rare” itself here, which is ”rado” in Italian. We are thus witness to a sporadic phonetic change, namely ”r → d” (Latin → Italian). We find it to be in the environment ”rV_” (”if /r/ is placed after /r/ plus a vowel”) here, but not always since no rule explains the change completely, thus making it sporadic.

If you would like to understand in depth the transition of the pronunciation from Latin to French, I will refer you to this link. Leave a comment below if you require more details, which I would be happy to provide.


There are four main triggers resulting in phonetic changes in a language:

  1. spontaneous innovation;
  2. reduced acoustic interference;
  3. the law of least effort of articulation;
  4. foreign influence.

Do you want an example of each? No trouble. However, the first case (spontaneous innovation) is a change which manages to propagate without justification, therefore an illustration wouldn’t convey much. Spontaneous innovation is sometimes motivated by will of cultural distinction. Theoretically, it could be that a single individual was cause of a phonetic innovation, but such an event has never been verified (after all, the first phonetic studies date back only up to 1889, to a time where we had just begun to master sound recording).

In the case of reduced acoustic interference, we could cite the disappearance of the sound of the letter L in the English words ”walk” and ”talk”. The sound /l/ being difficult to distinguish due to the nature of the sound of the letter A, the speaker hence considers it (unconsciously of course) to be optional, and skips it for the most part.

Cases concerning the law of least effort of articulation are without a doubt the most expressive. This law, or principle, is also called articulatory easing. It states that all sound simplifiable will be simplified. It is necessary to be prudent, however, with situations which prevent such simplification. For example, the sound /t/ could, in theory, become /d/ between two vowels (assimilation of vowel voicing on the consonant), but not if the sound /d/ already exists in the language*! This could explain why English transforms the sound /t/ to [ɾ] in this environment**.

* Unless there are some compensatory changes, and that, for example, the /d/ changes there as well: which is what we call a chain phonetic change, or shift. 

** A little more attention as I summarize; certain other phenomena are to be taken into account to draw precise conclusions -leave a comment below if you have any questions.

The following phenomena are related to easing of articulation:

  • apocope (abbreviation);
  • assimilation (fusion of the nature of the sound with the nature of the adjacent sound, for example the sound /ʁ/ in French which is pronounced [χ] after /t/ notably (like in ”trois”), so that the two consonants could have the same sonority;  
  • crasis (the fusion of two words together, such as with ”de le → del → du”);
  • elision (such as with ”le arbre → l’arbre”) ; 
  • lenition (the weakening of articulation of a sound, sometimes leading to its elision, such as ”portata (Latin) → portéde (Old French) → porte”).

Foreign influence can take place through loans. This was notably seen through German influence causing dialects from the north of France to replace the alveolar trill /r/ by the uvular trill /ʀ/, which became standard thereafter.

The principle of American Eight

Do you know American Eight? It is a card game akin to the War game of which the basic principle (I won’t be giving you the details here) stipulates that a player can place only a card of the same color or rank as the one preceding it. Thus a player can place only a seven or a heart on the seven of hearts (barring any special cards). While phonetics doesn’t have any special cards (or any cards really), the principle of the American Eight itself functions quite often; we only have to replace the card color with a mode of articulation and the rank with a point of articulation. While this is not a constant, a sound usually changes its point of articulation without changing the mode of articulation and vice versa.

A fitting example of this is French. Let’s see its history in the standard.

Evolution of the pronunciation of the French R.
  • In Latin, the letter is pronounced as /r/ (the alveolar trill);
  • from the French Revolution onwards, the dialect from Paris spreads, and their /ʀ/ becomes the standard (the uvular trill /ʀ/, also known as the ”guttural R” – that of Edith Piaf); 
  • during the 18th Century, the ease of articulation caused it to become /ʁ/ (voiced uvular fricative);
  • today, the norm is still /ʁ/, but sometimes due to ease of articulation we hear [ɰ̠] (voiced uvular spirant) or [ɐ̯] (pre-opened central vowel).

At each evolution of the sound, it’s possible to see that the mode of articulation (trill, fricative, spirant) or the point of articulation (alveolar, uvular) is conserved. On the table above, we note that evolution never changes the sound in the column and in the line at the same time.

The evolution towards the vowel [ɐ̯] (which is close to /a/) is explained by it being positioned at the same place as the consonant; the terminology changes because it’s a vowel and not a consonant, but the change is not a big one. German pronounces R and ER in that exact same way after a vowel : ” Feuer ” /foɪ̯ɐ/.

So, can you see how the sound /r/ (the trilled Spanish R) can become the vowel /a/? There would have been 100s of other details worth mentioning, but my goal wasn’t to write an essay. This article is just long enough, so please don’t hesitate to ask me questions in the comments and I will be happy to help! Thank you for reading!


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