Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
arc [ɑːk] n (also MATH) дуга́#
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
ARC n abbr
( = American Red Cross)
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.