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What is the ‘X’ Symbol? 6 Powerful Meanings

The most powerful letter in the alphabet, the symbol of X has been used in so many fields, from algebra to science, astronomy and spirituality. X represents the unknown, but it also has other meanings. Here’s what to know about the significance of the X symbol, along with its origin and history.

What Does ‘X’ Symbolize?

The X symbol has diverse meanings, representing the unknown, secrecy, danger, and the end. It can have mystical significance, as well as scientific, or linguistic importance. Here are some of the meanings of the symbol, along with its usage in various contexts.

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x in algebra

1. Symbol of the Unknown

In general, the X symbol is used to denote something mysterious or unknown, meant to be solved. In algebra, we’re often asked to solve x as a variable or a value that’s not yet known. In the English language, it’s commonly used to describe something vague. For example, we say Brand X or Mr. X. In some contexts, it’s also used for confidential documents, thing, person, or place. All this has given X the meaning of something that is mysterious and not known.

2. Symbol of the Known

Paradoxically, X can mean the complete opposite and represent the known. X is sometimes used for labeling specific locations or destinations on maps and meeting places. From this practice comes the saying x marks the spot. In fiction, it’s commonly found on treasure maps, showing where the hidden treasure is buried. It can also be used to mark the place where skydivers should land, or where actors should be on a stage.

X is also a universal signature for those who can’t read or write, indicating their identity, or agreement on a contract or document. Sometimes, it also marks the portion where a document should be dated or signed. Nowadays, we use it to indicate a choice, like marking X on a ballot or multiple choice exam.

3. Danger and Death

Some associate the X symbol with the overlapping femurs or the skull-and-crossbones that signify danger and death. While the crossbones first became associated with pirates, it later became a generalized hazard warning by the end of the 19th century.

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Later, both skull-and-crossbones and X symbol on an orange background became the standard for labeling harmful and toxic substances throughout Europe. It’s likely one of the reasons why the X symbol gained a macabre relationship with death.

4. Error and Rejection

Most of the time, the X symbol is used for the concept of error and rejection. For instance, it’s used to indicate wrong answer, especially on an exam, as well as a cancellation that requires a do-over.

5. End of Something

In some context, the symbol of X signifies an entity whose existence is over, past, and gone. In technical use, the letter X is often a shorthand version of a longer prefix ex. This is used to describe former relationships, such as ex-husband or ex-CEO.

6. A Kiss

In 1763, the Oxford English Dictionary included the definition of a kiss for the letter X. It was Winston Churchill who popularized the idea, when he signed off a letter in 1894 with the letter X. It might be because the letter X resembles two people kissing. How, you ask? Well, take a close look. The symbols > and < meeting like a kiss, create an X. Today, it’s widely used at the end of emails and text messages to signify a kiss.

skull and crossbones flag

History of the X Symbol

Before gaining its mystic significance, X was a letter in the early alphabet. Later, it was used to represent the unknown and a variety of concepts in mathematics and science.

In Alphabetic Symbolism

The first alphabet appeared when pictograms evolved into symbols that represented individual sounds. X is derived from the Phoenician letter samekh, which represented the /s/ consonant sound. After 200 years, from 1000 to 800 BCE, the Greeks borrowed the samekh and named it chi or khi (χ)—the twenty-second letter of the Greek alphabet from which X developed.

In Roman Numerals

The Romans later adopted the Chi symbol to denote the letter x in their Latin alphabet. The X symbol also appears in Roman numerals, a system of letters used for writing numbers. Each letter in the system stands for a number, and X represents 10. When a horizontal line is drawn above X, it means 1,000.

In Mathematics

In algebra, the X symbol is now used to represent an unknown variable, value, or quantity. In 1637, René Descartes used x, y, z for unknown variables to correspond to a, b, c used to denote known quantities. Just take note that a variable doesn’t have to be indicated by the letter x, as it could be any other letter or symbol. So, its use for representing the unknown might have a deeper and earlier origin.

Some speculate that the use of the x symbol in mathematical equations stemmed from the Arabic word shay-un that means something or undetermined thing. In ancient Islamic text Al-Jabr, a manuscript that established the rules of algebra, mathematical variables were referred to as undetermined things. It appears throughout the text to represent the part of the equation that’s not yet identified.

When the manuscript was translated by Spanish scholars, the Arabic word shay-un couldn’t be translated because Spanish has no sh sound. So, they used the closest sound, which is the Greek ch sound represented by the letter chi (χ). Eventually, these texts were translated into Latin, where the translators simply replaced the Greek chi (χ) with the Latin X.

In Science and Other Fields

x-ray hand

Because of its use in algebra, X became associated with the unknown. When physicist Wilhelm Röntgen discovered a new form of radiation in the 1890s, he called them X-rays because he didn’t fully understand them. In genetics, early researchers named the X chromosome because of its unique properties.

In aerospace, the x symbol stands for experimental or special research. In fact, each aircraft is recognized by a letter that designates its purpose. X-planes have accomplished several aviation firsts, from innovations to breaking altitude and speed barriers. Also, astronomers have long used X as the name of a hypothetical planet, a comet of unknown orbit, and so on.

Symbolism in Christianity

xmas bauble in snow

In the Greek language, the letter chi (χ) is the first letter in the word Christ (Χριστός) pronounced khristós. It means the Anointed One. Some sources say that Constantine may have seen the Greek letter in a vision, which led him to adopt the Christian faith. While some associate the X symbol with the cross, scholars say that the symbol is more identical to the pagan symbol for the sun.

Today, the X symbol is often used as a short form for Christ. As a graphical device or Christogram, it replaces the word Christ in Christmas, which is why we have Xmas. The other popular example is the Chi-Rho or XP, the first two letters of Christ in Greek superimposed over one another. In 1021 CE, the word Christmas was even abbreviated as XPmas by an Anglo-Saxon scribe to save some space in writing.

Some people are fond of symbols to represent their faith. However, the X symbol itself predates Christianity, as it was once the symbol of luck in ancient Greece. Some don’t like the use of X to represent Christ in Xmas, considering the many negative meanings of X. After all, it does mean unknown and error. But some argue that the controversy is only a misunderstanding of language and history.

In African Culture

For many African-Americans, slavery impacted their personal histories. If they didn’t know their surnames, it would simply be replaced with an X. For many Africans, X is a marker of absence, because some slaveowners never gave their slaves a name.

This is why Malcom X, an African American leader and supporter of Black nationalism, took the surname X in 1952. For him, it symbolized the unknown African name of his ancestors. He preferred it to his ‘slave’ name, as he put it. While this might come across as a bitter reminder of slavery, it’s a declaration of his African roots.

The Symbol of X in Modern Times

x files poster

The sense of mystery in the X symbol has led to its wide use in naming, from Malcom X to the Generation X, and sci-fi television series X-Files and X-Men.

Generation X

Why were those born between 1964 and 1981 called Generation X? Was it because they were young people whose future was uncertain? The term Generation X was first coined by Jane Deverson in a 1964 publication, and popularized by Canadian journalist Douglas Coupland in 1991’s novel, Generation X: Tales for an Accelerated Culture. This demographic is often described as a group of people who didn’t want to concern themselves with societal status, pressure and money.

In Pop Culture

X is everywhere in pop culture. Some examples include the following.

The sci-fi television series X-Files had a cult following in the 1990s. Who can forget that haunting introduction song? This series revolves around paranormal investigations, existence of extraterrestrial life, conspiracy theories, and paranoia about the US government.

In the Marvel comics and movie X-Men, the superheroes had an x-gene, which resulted in extra powers.

In Email and Social Media

Nowadays, the X symbol is widely used at the end of letters to indicate a kiss. Sometimes, the uppercase (X) signifies a big kiss, though it shouldn’t always be regarded as a sign of romantic gesture. Some people simply include it in messages to add a warm tone into it, making it common among friends. Together with O, which signifies a hug, you get XO.

In Brief

Each of the letters in the alphabet has a history, but X is the most potent and mysterious. Since its inception, it has been used to represent the unknown, and has more social and technical uses than any other letter in the English alphabet. Nowadays, we use the symbol in mathematics, to mark places on a map, to indicate our choice of candidates on a ballot, to indicate an error, and many more.

Symbolism of x
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Yordan Zhelyazkov
Yordan Zhelyazkov

Yordan Zhelyazkov is a published fantasy author and an experienced copywriter. While he has degrees in both Creative Writing and Marketing, much of his research and work are focused on history and mythology. He’s been working in the field for years and has amassed a great deal of knowledge on Norse, Greek, Egyptian, Mesoamerican, Japanese mythology, and others.