X

x UK [eks] / US or X UK / US noun [countable/uncountable]
Word forms "x":
singular x plural x's
Word forms "X":
singular X plural X's

1) the 24th letter of the English alphabet. X is a consonant.

2) maths used in mathematics for showing a number whose value you do not know

In this equation, X equals four.

3) used instead of saying the name of a person or place when you do not know it, or when you are using them as an example

Let us say Mr X gives a property to his son...

4) informal a symbol used for writing a kiss, usually at the end of a letter

5) the roman numeral for 10

6) used in the past for saying that a film was not suitable for people under the age of 18

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- X marks the spot