The Clue
Friedrich units, for short (3 letter answer)
The Answer
ACS
Tags
Notes
The answer ACS is common and appears about once every 325 puzzles.
Related Clues
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Chemists' org.
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160 sq. rd. units
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Definition
AC as a noun:
1. (actinium, Ac, atomic number 89) = a radioactive element of the actinide series; found in uranium ores
2. (alternating current, AC) = an electric current that reverses direction sinusoidally; "In the US most household current is AC at 60 cycles per second"