x

noun

ˈeks 

variants often X

plural x's or xs ˈek-səz 

often attributive

1

a

: 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

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Words Starting With X

Browse 436 words and phrases that start with the letter X, from Xanadu to xystus.

Examples of x in a Sentence

a word that starts with an x

a word that starts with x

Word History

First Known Use

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

Phrases Containing x

• x-axis
• x-coordinate
• x-height
• x-intercept
• x-irradiation
• x out
• x-radiation
• x-ray
• x-section

Kids Definition

x

1 of 3 noun

ˈeks 

often capitalized

1

: the 24th letter of the English alphabet

2

: ten in Roman numerals

3

: an unknown quantity

x

2 of 3 verb

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

1

: to mark with an x

2

: to cancel with a series of x's

X

3 of 3 adjective

ˈeks 

of a motion picture

: of such a nature that admission is denied to persons under a certain age (as 17)

—used before the adoption of NC-17

Medical Definition

x

1 of 2 noun

ˈeks 

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

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

x

2 of 2 symbol

1

capitalized halogen atom

—used in general formulas (as of trihalomethane CHX₃)

2

power of magnification

Legal Definition

x

1 of 2 noun

ˈeks 

often capitalized

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)

x

2 of 2 abbreviation

1

ex-distribution

2

ex-dividend

3

ex-rights

4

ex-warrants