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• Der 24. Buchstabe des englischen Alphabets, ein Konsonant. Er bezeichnet meist die Lautfolge /ks/ und ist einer der seltensten Buchstaben der Sprache. Er wird als römische Zahl 10, als Kusszeichen in Nachrichten, als Symbol für das Unbekannte in der Mathematik und als Abkürzung für 'extra' oder 'experimentell' verwendet.

The twenty-fourth letter of the English alphabet and the nineteenth consonant, representing the voiceless velar fricative and sibilant cluster /ks/ or /gz/. As a grapheme, 'X' is the third least common letter in English and is rarely seen at the beginning of words. It historically derives from the Greek letter Chi. It functions as the Roman numeral for 10, a symbol for a kiss in informal correspondence, an algebraic variable for an unknown quantity, and a designation for 'extra' or 'experimental'.

1. The twenty-fourth letter of the English alphabetA1formal

   The uppercase or lowercase character (X, x) that constitutes the twenty-fourth symbol in the Latin-based English alphabet, classified as a consonant. It most often represents the consonant cluster /ks/. It is the third least common letter in English, and words beginning with X are often of Greek origin. It is unique for its strong association with mathematical notation and pop culture symbols.

   Vierundzwanzigster Buchstabe des englischen Alphabets

   • The word 'xylophone' begins with the letter X.
   • In the word 'exit', the letter X is pronounced as /ks/.
   • X is one of the rarest letters in the English alphabet.
   • The NATO phonetic word for X is 'X-ray'.
   • The pirate map had a large red X marking the spot.

2. The Roman numeral for 10A2formal

   The symbol X used in the Roman numeral system to represent the cardinal number ten (decem in Latin). It is a fundamental component for constructing numbers from 9 (IX) to 39 (XXXIX) and beyond in combination with other symbols. It is widely seen on clock faces, movie sequels, and formal event numbering.

   Römische Ziffer 10

   • Super Bowl X was played in 1976.
   • Chapter X is the final chapter of the book.
   • The clock face uses X for the number 10.
   • The number 29 in Roman numerals is written as XXIX.
   • Pope Leo X was a member of the Medici family.

3. A symbol for a kissA2informal

   The letter X used as a symbolic representation of a kiss in informal written correspondence, such as letters, greeting cards, and text messages. It often appears in sequences (e.g., 'XXX') and is frequently paired with 'O', which symbolizes a hug. This tradition originated in medieval times, when an X was used to sign documents as a mark of sincerity, with the signer then kissing the mark.

   Kuss (in der Korrespondenz)

   • She signed off her text with 'Love you, XOXO'.
   • I'll miss you! Sending lots of Xs and Os.
   • The card ended with a simple 'X' from a secret admirer.
   • Put an X at the bottom of the letter for a kiss.
   • Her emails to her mom always end with three X's.

4. The symbol for an unknown variable in mathematicsA2formalscientific

   The lowercase letter x used as the standard symbol for an independent, unknown, or variable quantity in algebra, analytic geometry, and calculus. It is the most iconic mathematical symbol, solving for x being tantamount to finding a solution. It originated from the Arabic word 'shay' (thing), translated into Spanish as 'xei', which was later abbreviated to x.

   Unbekannte Variable (Mathematik)

   • Solve the equation for x: 2x + 3 = 7.
   • The x-axis runs horizontally on a graph.
   • If f(x) = x², find the value of the function when x = 5.
   • The unknown quantity x is the key to the problem.
   • Algebra students spend a lot of time solving for x.

5. A designation for 'extra' or 'experimental'B1informal

   The letter X used as an abbreviation or prefix to denote something extra, extreme, or experimental. It commonly appears in product branding (e.g., iPhone X), clothing sizes (XL, XS), and entertainment ratings (X-rated). It evokes a sense of mystery, power, or the cutting edge, and is frequently leveraged in marketing to imply something advanced or forbidden.

   Extra, experimentell oder extrem

   • The X-Men team consists of mutants with extraordinary powers.
   • He bought a new iPhone X on the day of its release.
   • XL shirts provide extra room for a looser fit.
   • The movie was rated X for its extreme content.
   • The experimental aircraft was dubbed the X-15.