Hi, I'm "Craipig", the 'p' is silent, and this is Mental Floss on YouTube. Today I'm going to answer morgana7544's Big Question: "Why are there silent letters in English words?" Well, 7544 (can I call you that?), around 60 percent of English words contain a silent letter. Today I'm going to tell you why. Let's get started.

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So there's a couple of reasons why letters might be silent. Edward Carney, who wrote "A Survey of English Spelling", made this a little less confusing by dividing silent letters into two groups: auxiliary and dummy.

Auxiliary letters are the ones that you combine with another letter to make a unique sound. Auxiliary letters fall into two subcategories: exocentric and endocentric. Exocentric is when the sound isn't like either of the letters, like the 'ng' in 'king' or the 'th' in 'then'; it's not kiN-G or T-Hen. Endocentric is when the sound is the same as one of its letters, like in double-consonant, like the two 'm's in 'roommates' or the silent 'e' at the end of 'made'.

And then there are dummy letters. This is when the silent letter is really stupid – no, it's when it is unrelated to the letters around it and doesn't impact pronunciation. These also fall into two subcategories: inert letters and empty letters. Inert letters are part of a word segment and may not be silent in variations of the word. For instance, the 'g' in 'resign' is silent, but isn't silent in 'resignation'. Empty letters are never pronounced, like the 's' in "island" – oh, it's pronounced 'island'?

Now you know how to categorize silent letters, but the question still remains, why do we have them? Well, they emerge in the English language for a few different reasons, often, especially in the case with auxiliary letters, the silent letters were originally pronounced, but pronunciation changed over time without a spelling change.

For instance, in the middle ages, they pronounced both the 'k' and the 'g' in the word 'knight', as in K-niG-H-t. Really? That's amazing! Similarly, the silent 'w' in words like 'wrath' would indicate that the word was pronounced differently than words starting with 'r', but that pronunciation disappeared over time.

And, for many dummy letters, we can blame our ancestors for being snobby and adding in silent letters where they didn't previously exist. According to the Dictionary of Modern English Grammar, quote:

As the influence of the Classical world was revived in the 15th century, scholars of English desired to remind their readers that most of the words in the language originated in Latin and Greek. To show off their knowledge that doubt, then spelled 'dout' because it came into medieval English via French doute, derived originally from Latin dubitare they added the b – and it stuck.

Consonant clusters also developed over time. This is when a group of constanants is bunched together, but only contain one syllable, like the 's-t-h' in asthma. This happens a lot with words we borrow from other languages. For instance, the 'p-s' in 'psychology' comes from the Greek language.

Thanks for watching Mental Floss on YouTube, made with the help of these consonant clusters. If you have a Big Question of your own that you'd like answered, leave it below in the comments. See you next week.