noun, often capitalized, often attributive
\ˈeks \
plural x's or xs\ˈek-səz \

Definition of

(Entry 1 of 4)

1a : the 24th letter of the English alphabet

b : a graphic representation of this letter

c : a speech counterpart of orthographic x

2 : ten — see Table of Numbers

3 : a graphic device for reproducing the letter x

4 : one designated x especially as the 24th in order or class, or the first in an order or class that includes x, y, and sometimes z

5 : an unknown quantity

6 : something shaped like or marked with the letter X


x-ed also x'd or xed\ˈekst \; x-ing or x'ing\ˈek-siŋ \

Definition of (Entry 2 of 4)

transitive verb

1 : to mark with an x

2 : to cancel or obliterate with a series of x's usually used with out x-ed out the mistake

Definition of (Entry 3 of 4)

1 cross

2 ex

3 experimental

4 extra

\ˈeks \

Definition of (Entry 4 of 4)

of a motion picture

: of such a nature that admission is denied to persons under a specified age (such as 17) used before the adoption of NC-17

Examples of x in a Sentence


a word that starts with an x a word that starts with x

First Known Use of x


before the 12th century, in the meaning defined at sense 1a


circa 1849, in the meaning defined at sense 1


1970, in the meaning defined above

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Phrases Related to x

x out

Statistics for x

Look-up Popularity

Time Traveler for x

The first known use of x was before the 12th century

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Financial Definition of x

What It Is

X is an extension to a ticker symbol. It denotes that the security is a mutual fund.

How It Works

For example, Vanguard offers a variety of mutual funds. The tickers end in X.

Why It Matters

Many companies have several different types of securities listed. Extensions help investors understand which securities are which.

Source: Investing Answers



English Language Learners Definition of x

: the 24th letter of the English alphabet

: the Roman numeral that means 10

mathematics —used to represent an unknown quantity


noun, often capitalized
\ˈeks \
plural x's or xs\ˈek-səz \

Kids Definition of x

1 : the 24th letter of the English alphabet

2 : ten in Roman numerals

3 : an unknown quantity What is the value of x in the equation x + 2 = 6?

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\ˈeks \
plural x's or xs or x'es or xes\ˈek-səz \

Medical Definition of

(Entry 1 of 2)

: the basic or monoploid number of chromosomes of a polyploid series : the number contained in a single genome — compare n sense 1



Medical Definition of (Entry 2 of 2)

1 capitalized halogen atom used in general formulas (as of trihalomethane CHX3)

2 power of magnification


noun, often capitalized
\ˈeks \

Legal Definition of

(Entry 1 of 2)

1 : a mark used in place of a signature when the maker is incapable of signing his or her name (as because of illiteracy or a physical ailment)

2 : a mark used in indicating a choice or applicable item (as on an insurance form)

Legal Definition of (Entry 2 of 2)

1 ex-distribution

2 ex-dividend

3 ex-rights

4 ex-warrants

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More from Merriam-Webster on x

See words that rhyme with x

Spanish Central: Translation of x

Nglish: Translation of x for Spanish Speakers

Britannica.com: Encyclopedia article about x

Comments on x

What made you want to look up x? Please tell us where you read or heard it (including the quote, if possible).


not any or not one

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Great Scrabble Words—A Quiz

  • scrabble-tiles-that-read-scrabble-quiz
  • Which of the following Q-without-U words means the number five in cards or dice?
True or False

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