X (named ex , plural exes) is the twenty-fourth letter in the ISO basic Latin alphabet.

The .X file is a file extension used by many programs and programmers as a simple mesh file. It is a DirectX file that can be viewed in the DirectX Viewer, a program available with the 2008 DirectX June SDK (Software Development Kit). Although it is not the highest quality 3D file format, (not graphically enhanced, moderate quality) it is an efficient 3D model mesh file format because of how easy it is to load into programs and games.

AmiExpress - also known as /X - by Synthetic Technologies was a popular BBS software application for the Commodore Amiga line of computers. AmiExpress was extremely popular among the warez scene for trading (exchanging) software.

An emoticon is a pictorial representation of a facial expression using punctuation marks and letters, usually written to express a person's mood. Emoticons are often used to alert a responder to the tenor or temper of a statement, and can change and improve interpretation of plain text; emoticons for a smiley face :-) and sad face :-( appear in the first documented use in digital form. The word is a portmanteau word of the English words emotion and icon. In web forums,  instant messengers and online games, text emoticons are often automatically replaced with small corresponding images, which came to be called emoticons as well. Certain complex character combinations can only be accomplished in a double-byte language, giving rise to especially complex forms, sometimes known by their romanized Japanese name of kaomoji.

In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example,

The voiceless uvular fricative is a type of consonantal sound, used in some spoken languages. The symbol in the International Phonetic Alphabet that represents this sound is ⟨⟩, or in broad transcription ⟨⟩ although the latter technically represents a velar pronounciation. The sound is represented by ⟨⟩ (ex with underdot) in Americanist phonetic notation.