奶奶

English uses one word, grandma, for both sides of the family, but Chinese does not. 奶奶 is specifically your father's mother, never your mother's mother. Your mother's mother gets a different kinship word, often 外婆 or 姥姥 depending on region. If you call your mom's mom 奶奶, relatives will immediately correct you. “爸爸的妈妈叫奶奶。” (Daddy's mommy is called Grandma (nǎinai).) ── [《我的家人（1）》](/read/my-family-members-1#s4)

English lets you say go to Grandma's without saying house. Chinese does not. 去奶奶 sounds like you are going to Grandma as a destination object. Say 去奶奶家 or 去奶奶那儿. For a visit, 看奶奶 or 去看奶奶 works naturally.

Inside the family, 奶奶 means your dad's mom. Outside the family, calling an elderly woman 奶奶 is warm and respectful. It works like ma'am or granny without claiming blood relation. If you know her surname, 王奶奶 is very common. Do not use it for a young or middle-aged woman, because it points at age.

Reduplicated family words often lighten the second syllable in real speech. 奶奶 is nǎi nai, not nǎi nǎi. The same rhythm shows up in 爷爷, 爸爸, and 妈妈. If you hit both third tones hard, it sounds like you are reading a dictionary.