Percentage

https://en.wikipedia.org/wiki/Percentage

• A percentage is a number or ratio expressed as a fraction of 100

• It is often denoted using the percent sign, %.

• A percentage is a dimensionless or pure number.

• 45% (read "forty-five percent") = 45/100 = 45:100 = 0.45

• Percentages are often used to express a proportionate part of a total.

• the term "percent" is derived from the Latin per centum "by the hundred"

• the percent symbol evolved by gradual contraction of the Italian per cento "for a hundred". "per" was often abbreviated as "p." and eventually disappeared; "cento" was contracted to two circles separated by a horizontal line, which evolved into the modern symbol.

Parts per $10^i$ where $i=\{2,3,4\}$

• $\%$ indicates parts per hundred, $10^2$ % (percent), ﹪ % ％

• $‰$ indicates parts per thousand, $10^3$ ‰

  • spelled: per mil, per mill, permil, permill, permille, promille

• $‱$ indicates parts per ten thousand, $10^4$ ‱