Xi3

xi3 is a designation that can refer to several unrelated concepts, and it does not have a single, canonical definition. Depending on context, xi3 may denote mathematical notation, a syllable in Chinese romanization, or a product name used in technology.

In mathematics and statistics, xi (often written as ξ) is a common symbol for vectors or random variables. Subscripts such as 3, yielding ξ3 or xi3, typically designate the third component of a vector or a particular variable within a set. The exact meaning depends on the field, the notation used, and how the variables are defined in a given model or equation.

In linguistics and Chinese pinyin transcription, xi3 may appear to indicate the syllable xi with the third (falling) tone when digits are used to mark tones. In standard pinyin with diacritics, the same syllable is written xiǐ or xǐ for third-tone pronunciation, depending on the character. Examples of common characters pronounced xi in the third tone include 喜 (xǐ, joy) and 洗 (xǐ, wash). The digit notation xi3 is seen in some linguistic corpora and instructional materials.

In technology, Xi3 Corporation is a company known for producing small form factor modular personal computers. Its Xi3 modular computer line gained public attention around the early 2010s and is historically noted for its association with Valve's early Steam Box prototype efforts, where a Xi3 system was used as a reference design in demonstrations.