Record mathematical operation (3)
I believe the answer is:
log
I believe this is a double definition.
'record' is the first definition.
(logging is a kind of recording)
'mathematical operation' is the second definition.
(short for logarithm)
(Other definitions for log that I've seen before include "A ship or plane's diary" , "Piece of wood for the fire" , "Register" , "number in maths class?" , "Record kept" .)