ELI5: Explain Like I'm 5

Phonological history of English consonant clusters

Okay, so let's pretend you're playing with blocks. You know how sometimes you like to stack one block on top of another block to make a tall tower? Well, English words are kind of like towers made out of sounds called phonemes.

Consonants are certain sounds we make by blocking or squeezing the air that comes out of our mouths. So ‘t’ is a consonant sound, as is ‘p’ and ‘s,’ for example. A cluster happens when two or more of these consonant sounds are stuck together in a word.

Now, over time, the way people talked changed, and this affected the way English words sound. For example, the way we say ‘knight’ today is different from how people said it hundreds of years ago.

One type of change that happened is called cluster simplification. This is when people started getting lazy with their tongues and decided it was too hard to say a really complicated cluster of consonants in the middle of a word.

For example, the word ‘knee’ used to be ‘cnéow’ in Old English, but eventually people just started saying ‘knee’ instead. ‘Wrist’ used to be ‘wríst’ with both the ‘w’ and the ‘r’ pronounced separately, but now we just say ‘rist.’

Another type of change that happened is called cluster reduction. This is when people started dropping one of the consonant sounds in a cluster, so it became easier to say.

For example, the word ‘ghost’ used to be ‘gást’ in Old English, but over time the ‘h’ got dropped so we just say ‘ghost’ now. Similarly, ‘lamb’ used to be ‘lambu’ in Old English, but the ‘b’ got dropped and now we just say ‘lam.’

So there you have it, a very simplified explanation of how the way we talk has changed over time, and how that affected the way words sound, especially with clusters of consonants.