r

1. radius
2. or R Electricity resistance

1. Abbr. for “radius.”
2. Abbr. for “right.”
3. Symbol for the capacity of a pile (for example, 3R indicates three times design capacity). 4. Symbol for the thermal resistance of a material or component of construction.
5. Symbol for electrical resistance.

racemic

The noun has one meaning:

Meaning #1: the length of a line segment between the center and circumference of a circle or sphere
  Synonym: radius