any single character or series of characters that represents horizontal or vertical space in typography
In computer science, whitespace is any single character or series of characters that represents horizontal or vertical space in typography. When rendered, a whitespace character does not correspond to a visual mark, but typically does occupy an area on a page.
The term "whitespace" is based on the assumption that the background color used for rendered text is white.
As is common in technical literature, the two words "white space" have found widespread usage as the single term "whitespace", especially when used as an adjective, as in "whitespace character". Some specifications refer to "white space" while others refer to "whitespace"; there is no difference between the terms, although exactly which characters are being referred to does vary from context to context. For example, the form feed character is "whitespace" in HTML, but is not "white space" in XML.
Questions having the white-space tag regards the User Experience of whitespaces