Dear Geist,

Can you please explain, in terms that a gerbil could understand, when to capitalize Dad and Mum, and when not to, and why?

Dear Hinata,

Capitalize Dad, Mum, Father, Mother and so on when the word is a proper noun—that is, used in place of a name: “Last week Dad walked around the lake.” Lowercase them when they are not names: “My mother and I spent the whole afternoon at the library.”

Gerbils are inquisitive, playful and not easily startled, and they have fur on their tails. But I'm afraid we cannot know whether any gerbil would understand the information in this post.