Epistolary is an adjective that means related to a letter.

The Latin word epistola (ay pee STOLE uh) means a letter. This word gave birth to its English equivalent epistle, meaning ‘letter.’ Our word of the day is the adjective version of this word, indicating something related to an epistle or a letter.

My favorite novels are told in epistolary form. There’s something about the exchange of letters that makes a literary work intimate.