Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
tonic [ˈtɔnɪk] n (MED) тонизи́рующее сре́дство; (also: tonic water) то́ник; (MUS) то́ника
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: