This is the 850th most frequent Chinese word.
妈妈
Mother.
In this sentence, '妈妈' refers to the speaker's mother and serves as the subject of the sentence.
妈妈很喜欢喝茶。
Mom loves drinking tea.
Here, '妈妈' is used in the possessive form to indicate the birthday belongs to the mother.
今天是妈妈的生日。
Today is Mom's birthday.
In this case, '妈妈' represents the person accompanying the speaker in an activity.