This is the 11274th most frequent Russian word.
деда
"Деда" means "grandfather" (informal or affectionate form) in English.
'Деда' is used here in the colloquial Genitive form for 'дед' (grandpa), indicating possession of the book.
Книга принадлежит деда.
The book belongs to grandpa.
'Деда' is used here as the Accusative case of 'дед', showing the direct object of the action.
Вчера я встретил деда на улице.
Yesterday I met grandpa on the street.
'Деда' is used here in the Genitive case to indicate the source of advice.