This is the 798th most frequent Russian word.
мама
Mother.
Here, 'мама' is used as the subject of the sentence, indicating the main actor performing the action of cooking.
Моя мама готовит вкусный обед.
My mom is cooking a delicious lunch.
In this sentence, 'мама' is in the dative case ('маме'), indicating the indirect object whom the letter was given to.
Я передал письмо маме.
I handed the letter to mom.
In this instance, 'мама' takes the instrumental case ('мамой'), which is used after the preposition 'с' to indicate with whom the subject was speaking.