Five nines

Five nines, commonly taken to mean "99.999%", may refer to:
 * High availability of services, when the downtime is less than 5.25 minutes per year or 5 minutes and 15 seconds per year
 * Nine (purity), a 99.999% pure substance
 * German 15 cm artillery shells used in World War I
 * Five Sigma, or Standard Deviations of physical rigor required to make a significant stake claim about the fundamental nature of the cosmos, shared reality, and everything.