This is the 11705th most frequent Russian word.
заведующая
"Заведующая" in English means "female manager" or "female head of a department."
Here, 'заведующая' refers to a female manager or head of a department, used in nominative case.
Новая заведующая приняла поздравления от коллектива.
The new manager received congratulations from the team.
In this instance, 'заведующей' is in the dative case, indicating the entity receiving an action.
Я позвонил заведующей клуба, чтобы уточнить правила.
I called the manager of the club to clarify the rules.
Again, 'заведующей' is used in the dative case, showing to whom the letter is addressed.