Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
radish [ˈrædɪʃ] n (one radish) реди́ска#
radishes реди́с msg, реди́ска fsg (разг)
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: