What is the ‘X’ Symbol? 6 Powerful Meanings

The X symbol holds immense significance across multiple fields, from mathematics to science, linguistics, spirituality, and even pop culture. While X often represents the unknown, it also conveys certainty in other contexts. Below, we explore the various meanings behind X and how it evolved into one of the most powerful and versatile symbols in modern culture.

What Does ‘X’ Symbolize?

The X symbol carries a range of meanings, such as mystery, secrecy, danger, endings, and affection. Let’s explore its different uses across contexts and traditions.

x in algebra

1. Symbol of the Unknown

The X symbol represents mystery and invites us to solve it. In algebra, mathematicians use X as a variable to denote an unknown value waiting to be discovered. In language, X refers to vague or undefined concepts—like “Brand X” or “Mr. X.” It also denotes secrecy, such as in classified documents labeled “Project X.” In all these contexts, X embodies enigma, suggesting something hidden or unresolved.

2. Symbol of the Known

Paradoxically, X can also mark the known. On maps, “X marks the spot” to show exact locations, a phrase popularized by treasure maps in fiction. Skydivers use X to mark landing zones, and theater directors place X on stage to indicate where actors should stand. These uses highlight X as a symbol of certainty and precision, guiding people to specific points.

X also acts as a signature for those who cannot read or write, representing personal identity on contracts and legal documents. In modern use, X marks selections—such as on ballots or multiple-choice exams—to express decisions and preferences.

3. Danger and Death

The X symbol gained its association with danger through its connection to skull-and-crossbones imagery, which pirates first used to signal threat or death. Over time, authorities adopted the symbol as a general hazard warning. In 19th-century Europe, regulators further strengthened its link to danger by pairing the X symbol with an orange background to label toxic substances. This usage cemented the symbol’s connection to poison, death, and danger across various industries.

4. Error and Rejection

People often use the X symbol to indicate error or rejection. Teachers mark incorrect answers with X on exams to signal mistakes that need correction. In printed documents, people use X to cancel errors, indicating that a revision or do-over is required. The symbol also appears on checklists to mark tasks that failed to meet standards or criteria.

In some settings, X signifies disapproval or failure, such as when a product is marked with an X to show it did not pass quality control. This association with rejection extends into digital interfaces, where X buttons close windows or cancel commands. Across contexts, X communicates the need for correction, rejection, or elimination, reinforcing its symbolism as a marker of errors.

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, mathematicians now use X to represent an unknown variable, value, or quantity. In 1637, René Descartes popularized the use of x, y, and z for unknowns, pairing them with a, b, and c to denote known quantities. Variables don’t need to be represented by the letter X; mathematicians can use any symbol to represent unknowns. However, the choice of X likely stems from deeper historical origins.

Some scholars trace the use of X in mathematics to the Arabic word “shay-un,” meaning “something” or “undetermined thing.” In Al-Jabr, a foundational Islamic manuscript on algebra, mathematicians described variables as undetermined elements. When Spanish scholars translated the text, they struggled to pronounce “shay-un” because Spanish lacks the ‘sh’ sound. To solve this, they used the closest phonetic equivalent, the Greek letter chi (χ). Later, Latin translators replaced χ with X, cementing its use as a symbol for unknown variables in modern mathematical equations.

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. 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.

The X symbol today often serves as a short form for Christ. It functions as a Christogram, a graphical symbol used to replace the word “Christ” in certain contexts—most notably in the abbreviation Xmas. This practice derives from the Greek letter chi (χ), the first letter of the Greek word for Christ (Χριστός, pronounced “Khristos”). Another well-known Christogram is the Chi-Rho (XP), which combines the first two Greek letters of Christ’s name into a single symbol, frequently used in early Christian art and inscriptions.

In 1021 CE, an Anglo-Saxon scribe abbreviated Christmas as XPmas to conserve space, demonstrating that Christograms have been part of Christian writing for centuries. Although some people today view the abbreviation Xmasas secular or disrespectful, scholars emphasize that it remains deeply rooted in Christian tradition. The X in Xmasrepresents Christ, not an attempt to remove him from the word, as it derives from the Greek chi (χ), the first letter of Χριστός (Christ).

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

Sociologists and writers coined the term Generation X to describe individuals born between 1964 and 1981. Jane Deverson introduced the term in a 1964 publication, and Canadian journalist Douglas Coupland later popularized it in his 1991 novel, Generation X: Tales for an Accelerated Culture.

Generation X actively rejected societal expectations and placed less importance on status, pressure, and wealth. Unlike previous generations, many of its members embraced individualism and prioritized personal fulfillment over traditional markers of success, such as career advancement or financial accumulation. Their approach reflected a deliberate detachment from mainstream societal norms, as they sought meaning and satisfaction on their own terms rather than conforming to social expectations.

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

People now use the X symbol at the end of messages to signify a kiss. The uppercase X often represents a big kiss, though it isn’t always meant romantically. Many people include it in texts or letters to add warmth or friendliness, making it a common gesture among friends. When paired with O, symbolizing a hug, the combination XO expresses both affection and closeness. This shorthand has evolved into a universal symbol of warmth and connection, transcending romantic intent to convey friendly gestures of care.

Wrapping Up

Every letter in the alphabet carries its own history, but X stands out as the most potent and mysterious. Since its creation, people have used X to represent the unknown, giving it a symbolic weight unmatched by any other letter in the English alphabet. Over time, its role has expanded into a variety of social and technical functions.

Today, X plays a key part in mathematics as a variable, marks locations on maps, represents choices on ballots, and identifies errors. Its versatility extends into many other areas, making X one of the most dynamic and widely used symbols across different fields.

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.