ANSI is the American National Standards Institute. It is a group in the United States that writes rules for how things should be made and tested, so products — especially electronic and scientific equipment — are safe and can work with each other. You will also hear ANSI in computing: Windows computers used a set of letters and numbers often called the ANSI character set, so older files and some programs still talk about ANSI encoding. Though actually, what Windows called ANSI was not always the official ANSI standard; people just got used to the name. Later, terminal colours called ANSI colours borrowed the name too. Ordinary speakers do not say ANSI in daily life. Engineers, software people, and people who write technical papers do.