Strikethrough
Strikethrough is a typographical presentation of words with a horizontal line through their center, resulting in this effect. Contrary to censored texts, the words remain readable. This presentation signifies one of two meanings. In ink-written, typewritten, or other non-erasable text, the words are a mistake and not meant for inclusion. When used on a computer screen, however, it indicates recently deleted information. It can also be used deliberately to imply a change of thought (as in epanorthosis).
Strikethrough is primarily used to mark text that is mistaken or to be removed. Historically, this has also been marked by placing dots under the letters to be ignored (Latin: punctum delens).
In quantum field theory, a slash through a symbol, such as ⱥ, is shorthand for γμaμ, where a is a covariant four-vector, the γμ are the gamma matrices, and the repeated index μ is summed over according to the Einstein notation.
In medieval manuscripts such as the Domesday Book, "strikethrough" of text with red ink often functions as highlighting similar to modern underline.
The HTML presentational inline element for strikethrough is <strike> or <s> This element was, however, deprecated in the 1999 HTML 4.01 standard, and replaced by the <del> tag, a semantic element representing deleted text, which user agents (typically web browsers) often render as a strikethrough.
In the HTML5 draft, there is no presentational element for strikethrough. However, there are two related semantic elements. Firstly, <s>, that is strikethrough in HTML 3 and 4, is redefined to mark text that is no longer correct, and secondly, <del> marks text that has been deleted, as it does in HTML 4.01.
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