Permille

A permille or per mille is a tenth of a percent or one part per thousand. It is written with the sign ‰, which looks like a percent sign (%) with an extra ₀ at the end. It is a stylized form of the three zeros in the denominator. For instance, 5‰ = 5/1000 = 0.005 = 0.5%
Permille notation is used in discussion of seawater salinity: the average salinity is 35‰.

When used to describe property taxation in the U.S., it is called the millage rate.

See also: percent and parts per million