15 words plagued by unusual silent letters

The scourge of spellers, silent letters are 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, from our friends at Vocabulary.com, are 15 words that prove that English spelling is far from rational.

1. CHTHONIC

dwelling beneath the surface of the earth

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

2. PHLEGM

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

The "g" sound 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

extinct flying reptile

The first part of this word is from pteron, Greek for "feather" or "wing." The second part comes from daktylos, meaning "finger."

4. MUSCLE

animal tissue consisting predominantly of contractile cells

It comes from Latin musculus, literally meaning "little mouse," but the "c" went silent when the word entered French.

5. MNEMONIC

of or relating to or involving the practice of aiding the memory

The word 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.

6. ASTHMA

respiratory disorder characterized by wheezing; usually of allergic origin

This word, dating from the late 14th century, used to be spelled as it is pronounced, asma. It was only in the 16th century that the "th" was reintroduced to the English spelling, to make it like the Latin and Greek spellings.

7. APROPOS

of an appropriate or pertinent nature

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

8. RECEIPT

an acknowledgment (usually tangible) that payment has been made

In the Anglo-French spoken by the Norman conquerors, the word 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. KNEAD

manually manipulate (someone's body), usually for medicinal or relaxation purposes

This 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.

10. HONEST

marked by truth

The root 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.

11. GNAW

bite or chew on with the teeth

This 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.

12. SUBTLE

difficult to detect or grasp by the mind or analyze

Like receipt, this 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

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

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

a meeting planned at a certain time and place

This is from the French phrase rendez vous, meaning "present yourselves." Following the French pronunciation, both the "z" and "s" go silent.

To learn about more words with unusual silent letters and to add them to your vocabulary-learning program, see the full list at Vocabulary.com.