permille

Also, permil, per mil, per mille, promille
1) per (every) thousand (Latin)
2) one thousandth

3) the fraction 1/1000

4) the decimal 0.001

5) the symbol ‰

Baseball batting averages are written as a permille.
Legal limits blood alcohol content for driving a road vehicle in some countries are 0.5‰ or 0.2‰.