The word “grandpa” or “grandfather” can be capitalized depending on how it is used in a sentence or title. When used generically in a sentence such as: “my grandpa said to visit him,” then the word grandpa is lowercase because it is a generic noun.
Correct: My grandpa is the best.
Correct: My grandfather loves me.
However, if you are addressing your grandpa directly, such as when asking a question, then you should capitalize the word grandpa.
Correct: Can I go to the movies, Grandpa?
Correct: Can I go to the movies, Grandfather?
The same holds true for any other names you might call your grandfather such as “papa” or “papap.”
For more title capitalization questions, use our free title capitalization tool here.