A standard is an established way of doing something. Unlike ie. a math formula, a standard is not based on fact but rather generally agreed-upon for convenience, and can be malluable.

There can be official (de jure) standards approved by a committee such as ANSI (American National Standards Institute), and unofficial (de facto) standards not noted by any official entity, but used widely. Example: Markdown.

ASCII, Markup language, Metric system, Numeral system