15 Words Plagued by Unusual Silent Letters

Silent letters are the scourge of spellers and often a stumbling block when learning how to write in English. To the modern eye, it’s unclear what these letters are doing in the words in question, and learners sometimes simply have to memorize them. But the silent letters are very often hidden remnants of how the words passed through different languages on their way to English. Here are 15 words that prove that English spelling is far from rational.

1. Chthonic

Definition: “dwelling beneath the surface of the earth”

Greek-derived words often feature tricky consonant clusters that don't get pronounced that way in English. The word chthonic (from Greek kthon, meaning “earth”), tends to lose its initial “k” sound and ends up sounding like thonic.

2. Phlegm

Definition: “expectorated matter; saliva mixed with discharges from the respiratory passages; in ancient and medieval physiology it was believed to cause sluggishness”

The “g” sound in phlegm was lost when Latin phlegma became Old French fleume. But the silent g still gets pronounced in variations on the word, such as phlegmatic, which means “showing little emotion.”

3. Pterodactyl

Definition: “extinct flying reptile”

The first part of the word pterodactyl is from pteron, Greek for “feather” or “wing.” The second part comes from daktylos, meaning “finger.”

4. Muscle

Definition: “animal tissue consisting predominantly of contractile cells”

The word muscle comes from Latin musculus, literally meaning “little mouse,” but the c went silent when the word entered French.

5. Mnemonic

Definition: “of or relating to or involving the practice of aiding the memory”

The word mnemonic is from the Greek mnemonikos, “pertaining to memory.” The mn- consonant cluster proved too tricky in the languages that have borrowed the word and was simplified to an “n” sound. (Now that you know that, check out some mnemonic tricks and sentences to boost your knowledge.)

6. Asthma

Definition: “respiratory disorder characterized by wheezing; usually of allergic origin”

The word asthma, which dates from the late 14th century, used to be spelled as it is pronounced, asma. It was only in the 16th century that the t and h were reintroduced to the English spelling, to make it like the Latin and Greek spellings.

7. Apropos

Definition: “of an appropriate or pertinent nature”

The word apropros is from French, like rendezvous and faux below, where final consonants are often silent.

8. Receipt

Definition: “an acknowledgment (usually tangible) that payment has been made”

In the Anglo-French spoken by the Norman conquerors, the word receipt was spelled receite. The spelling eventually changed in English to add a p (bringing it into line with the Latin root recepta), but the pronunciation stayed the same.

9. Honest

Definition: “marked by truth”

The root of honest is Latin honestus, meaning “honorable,” ultimately from honos, also the source of honor. And like honor, the initial “h” sound was lost in the French versions of the word on their way to English.

10. Gnaw

Definition: “bite or chew on with the teeth”

The word gnaw started out in Old English as gnagan. Just as kn- words from earlier eras of English lost their k, gn- words were also simplified to the “n” sound.

11. Knead

Definition: “manually manipulate (someone’s body), usually for medicinal or relaxation purposes”

The word knead comes from the Old English verb cnedan and Middle English kneden. But like other kn- words, including knight and know, the k went silent in Modern English.

12. Subtle

Definition: “difficult to detect or grasp by the mind or analyze”

Like receipt, subtle is what happens when you make the spelling imitate Latin but forget about the pronunciation. French had lost the b in Latin subtilis (“fine”), resulting in sotil, which was then remade to look (but not sound) like the Latin original.

13. Solemn

Definition: “dignified and somber in manner or character and committed to keeping promises”

As with phlegm above, the silent n in solemn gets pronounced in related words like solemnity.

14. Faux

Definition: “not genuine or real; being an imitation of the genuine article”

In Old French, Latin falsus (“false”) became fals or faus, eventually leading to faux with a silent x.

15. Rendezvous

Definition: “a meeting planned at a certain time and place”

This word comes from the French phrase rendez vous, meaning “present yourselves.” Following the French pronunciation, both the z and s go silent.

A version of this story was created in 2014 in partnership with Vocabulary.com; it has been updated for 2023.