Sound changes: consonants

Languages change all the time. Words, of course, are the most obvious illustration of this, especially when we look at slang and such. Grammar, by contrast, tends to be a bit more static, but not wholly so; English used to have noun case, but it no longer does.

The sounds of a language fall into a middle ground. New words are invented all the time, while old ones fall out of fashion, but the phonemes that make up those words take a longer time to change. This does, however, occur more often than wholesale grammatical alterations. (In fact, sound change can lead to changes in grammar, but it’s hard to see how the opposite can happen.)

This brief miniseries will detail some of the main ways sounds can change in a language. The idea is to give you, the conlanger, a new tool for making naturalistic languages. I won’t be covering everything here—I don’t have time for that, nor do you. Examples will be necessarily brief. The Index Diachronica is a massive catalog of sound changes that have occurred in real-world languages, and it’s a good resource for conlangers looking for this sort of thing.


We’ll start by looking at some of the main sound changes that can happen to consonants. Yes, some effects are equally valid for consonants and vowels, but I had to divide this up somehow.


Lenition is one of the most common sound changes. Basically, it’s a kind of “weakening” of a consonant into another. Stops can weaken into affricates or fricatives, for instance; German did this after English and its relatives broke away, hence “white” versus weiß. Another word is “father”, which shows two examples of this—compare it to Latin pater, which isn’t too far off from the ancestral form. (Interestingly, you can even say that “lenition” itself is a victim.)

Fricatives can weaken further into approximants (or even flaps or taps): one such change, of /s/ to /h/, happened early on in Greek, hence “heptagon”, using the Greek-derived root “hepta-“. Latin didn’t take this particular route, giving us “September” from Latin septem “seven”.

Approximants don’t really have anywhere to go. They’re already weak enough as it is. The only place for them to go is away, and that sometimes happens, a process called elision. Other sounds can be elided, but the approximants are the most prone to it. In English, for instance, we’ve lost /h/ (and older /x/) in a lot of places. (“im” for “him” is just the same process continuing in the present day.)

Lenition and elision tend to happen in two main places: between vowels and at the end of a word. Those aren’t the only places, however.


Assimilation is when a sound becomes more like another. This can happen with any pair of phonemes, but consonants are more susceptible, if only because they’re more likely to be adjacent.

Most assimilation involves voicing or the point of articulation. In other words, an unvoiced sound next to a voiced one is an unstable situation, as is a cluster like /kf/. Humans are lazy, it seems, and they want to talk with the least effort possible. Thus, disparate sequences of sounds like /bs/ or /mg/ tend to become more homogenized. (Good examples in English are all those Latin borrowings where ad- shows up as “al-” or “as-“, like “assimilation”.)

Obviously, there are a few ways this can play out. Either sound can be the one to change—/bs/ can end up as /ps/ or /bz/—but it tends to be the leading phoneme that gets altered. How it changes is another factor, and this depends on the language. If the two sounds are different in voicing, then that’ll likely shift first. If they’re at different parts of the vocal tract, then the one that changes will slide towards the other. Thus, /bs/ will probably come out as /ps/, while /mg/ ends up as /ŋg/.

Assimilation is also one way to get rid of consonant clusters. Some of the consonants will assimilate, then they’ll disappear. Or maybe they won’t, and they’ll create geminates, as in Italian


Anyone who’s ever heard the word “ask” pronounced as “ax” can identify metathesis, the rearranging of sounds. This can happen just about anywhere, but it often seems to occur with sound sequences that are relatively uncommon in a language, like the /sk/ cluster in English.

This one isn’t quite as systematic in English, but other languages do have regular metathesis sound changes. Spanish often swapped /l/ and /r/, for example, sometimes in different syllables. One common thread that crosses linguistic barriers involves the sonority hierarchy. A cluster like /dn/ is more likely to turn into /nd/ than the other way around.

Palatalization, etc.

Any of the “secondary” characteristics of a consonant can be changed. Consonants can be palatalized, labialized, velarized, glottalized, and so on. This usually happens because they’re next to a sound that displays one of those properties. It’s like assimilation, in a way.

Palatalization appears to be the most common of these, often affecting consonants adjacent to a front vowel. (/i/ is the likely culprit, but /e/ and /y/ work, too.) Labialization sometimes happens around back rounded vowels like /u/. Glottal stops, naturally, tend to cause glottalization, etc. Often, the affecting sound will disappear after it does its work.


Dissimliation is the opposite of assimilation: it makes sounds more different. This can occur in response to a kind of phonological confusion, but it doesn’t seem to be very common as a regular process. Words like “colonel” (pronounced as “kernel”) show dissimilation in English, and examples can be found in many other languages.

Even more…

There are a lot of possible sound changes we haven’t covered, and that’s just in the consonants! Most of the other ways consonants can evolve are much rarer, however. Fortition, for example, is the opposite of lenition, but instances of it are vastly outnumbered by those of the latter.

Vowels present yet more opportunities to change up the sound of a language, and we’ll see them next week. Then, we’ll wrap up the series by looking at all the other ways the sound of a word can change over time.

Leave a Reply

Your email address will not be published. Required fields are marked *