grandfather

• Russian
  де́душкаdeduška

  ˈdʲedʊʂkəinherited

  The plain дед is more casual ('old man, grandpa').

• Ukrainian
  дідdid

  dʲidinherited
• Polish
  dziadek

  ˈdʑadɛkinherited
• Czech
  dědeček

  ˈɟɛdɛtʃɛkinherited

  Colloquially děda.

• Bosnian-Croatian-Serbian
  djed / dedaдјед / деда

  djedinherited

  Ekavian usage prefers deda to the plain ded.

• English
  grandfather

Sound laws at work

• Jat (ě) and its reflexes
• Polish vowel ablaut (ě → a, e → o)
• Ukrainian і (ikavism)