What is the 'X' Symbol? 6 Powerful Meanings (2025)

TheX symbolholds immense significance across multiple fields, frommathematics to science, linguistics, spirituality, and evenpop culture. While X often represents theunknown, 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?

TheX symbolcarries a range of meanings, such asmystery, secrecy, danger, endings, and affection. Let’s explore its different uses across contexts and traditions.

1.Symbol of the Unknown

TheX symbolrepresents mystery and invites us to solve it. Inalgebra, mathematicians use X as a variable to denote an unknown value waiting to be discovered. Inlanguage, 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 embodiesenigma, 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 bytreasure mapsin fiction.Skydiversuse X to mark landing zones, andtheater directorsplace X on stage to indicate where actors should stand. These uses highlight X as a symbol ofcertainty and precision, guiding people to specific points.

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

3. Danger and Death

TheX symbolgained its association with danger through its connection toskull-and-crossbones imagery, which pirates first used to signal threat or death. Over time, authorities adopted the symbol as ageneral hazard warning. In19th-century Europe, regulators further strengthened its link to danger by pairing theX symbolwith anorange background to labeltoxic substances. This usage cemented the symbol’s connection topoison, death, and dangeracross various industries.

4. Error and Rejection

People often use theX symbolto 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.

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 useXto represent an unknown variable, value, or quantity. In1637, René Descartes popularized the use ofx, y, and zfor unknowns, pairing them witha, b, and cto denote known quantities. Variables don’t need to be represented by the letterX; mathematicians can use any symbol to represent unknowns. However, the choice ofXlikely stems from deeperhistorical origins.

Some scholars trace the use ofX in mathematicsto theArabic word “shay-un,”meaning “something” or “undetermined thing.” InAl-Jabr, a foundational Islamic manuscript on algebra, mathematicians described variables as undetermined elements. WhenSpanish scholarstranslated the text, they struggled to pronounce “shay-un” becauseSpanish lacks the ‘sh’ sound.To solve this, they used the closest phonetic equivalent, theGreek letter chi (χ).Later,Latin translatorsreplacedχwithX, cementing its use as a symbol for unknown variables in modern mathematical equations.

In Science and Other Fields

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

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.

TheX symboltoday often serves as ashort form for Christ. It functions as aChristogram, a graphical symbol used to replace the word “Christ” in certain contexts—most notably in the abbreviationXmas. This practice derives from the Greek letterchi (χ), the first letter of the Greek word for Christ (Χριστός, pronounced “Khristos”). Another well-known Christogram is theChi-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.

In1021 CE, anAnglo-Saxon scribeabbreviatedChristmasasXPmasto conserve space, demonstrating that Christograms have been part of Christian writing for centuries. Although some people today view the abbreviationXmasas secular or disrespectful, scholars emphasize that it remains deeply rooted inChristian tradition. TheXinXmasrepresentsChrist, not an attempt to remove him from the word, as it derives from the Greekchi (χ), the first letter ofΧριστός(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

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 termGeneration Xto describe individuals born between1964 and 1981. Jane Deverson introduced the term in a1964 publication, and Canadian journalistDouglas Couplandlater popularized it in his 1991 novel,Generation X: Tales for an Accelerated Culture.

Generation X activelyrejected societal expectationsandplaced less importance on status, pressure, and wealth. Unlike previous generations, many of its membersembraced individualismandprioritized personal fulfillmentover traditional markers of success, such as career advancement or financial accumulation. Their approach reflected a deliberatedetachment 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 theX symbolat the end of messages to signify a kiss. The uppercaseXoften 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 withO, symbolizing a hug, the combinationXOexpresses 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, butXstands 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 inmathematicsas a variable, markslocations on maps, represents choices onballots, and identifieserrors. Its versatility extends into many other areas, making X one of the most dynamic and widely used symbols across different fields.