noun, often capitalized, often attributive
\ ˈeks How to pronounce x (audio) \
plural x's or xs\ ˈek-​səz How to pronounce xs (audio) \

Definition of x

 (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 How to pronounce xed (audio) \; x-ing or x'ing\ ˈek-​siŋ How to pronounce x'ing (audio) \

Definition of x (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 outx-ed out the mistake

Definition of x (Entry 3 of 4)

1 cross
2 ex
3 experimental
4 extra
\ ˈeks How to pronounce X (audio) \

Definition of X (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

Noun 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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Time Traveler for x

Time Traveler

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

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Statistics for x

Last Updated

24 Jan 2020

Cite this Entry

“X.” The Merriam-Webster.com Dictionary, Merriam-Webster Inc., https://www.merriam-webster.com/dictionary/xes?pronunciation&lang=en_us&dir=x&file=xes0001m. Accessed 28 January 2020.

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More Definitions for x

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

How to pronounce X (audio)

English Language Learners Definition of x

: the 24th letter of the English alphabet
: the Roman numeral that means 10
used to represent an unknown quantity


noun, often capitalized
\ ˈeks How to pronounce x (audio) \
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 How to pronounce x (audio) \
plural x's or xs or x'es or xes\ ˈek-​səz How to pronounce xes (audio) \

Medical Definition of x

 (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 x (Entry 2 of 2)

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


noun, often capitalized
\ ˈeks How to pronounce x (audio) \

Legal Definition of x

 (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 x (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

Rhyming Dictionary: 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).


showing steady, earnest care and effort

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