This is the 74th most frequent Ukrainian word.
дітей
The Ukrainian word "дітей" means "children" (genitive plural form).
In this sentence, 'дітей' is the plural form of 'child' ('дитина') in the genitive case, used to indicate the quantity.
У школі багато дітей.
There are many children in the school.
Here, 'дітей' is also the plural form in the genitive case, used after the preposition 'про' to indicate the object of care.
Вона піклується про дітей.
She cares for the children.
In this case, 'дітей' is the plural form in the genitive case, denoting possession ('of the children').