This is the 724th most frequent Serbian word.
децом
"Децом" means "with children" in English.
The word 'децом' (with the children) is used in the instrumental case to indicate the company with which the action is performed.
Играм се с децом у парку.
I play with the children in the park.
The word should be corrected to 'деци' (to the children) in the dative case to indicate the target of the verbal action.
Причајте ми о децом коју сте видели.
Tell me about the children you have seen.
The word 'децом' is used again in the instrumental case, showing an instrumental connection, here in relation to the state of satisfaction.