Epistolary (adjective)

1. Relating to or suitable for writing or receiving letters.
2. Written in the form of or as if in the form of letters or correspondence.

Origin:

From the latin epistolarius, from epistola "letter".

Examples:

1. An epistolary novel is written in the form of letters.
2. The epistolary form is a literary device that uses letters to tell a story.
3. An epistolary relationship is one conducted through letters.
4. Epistolary is a literary style that is written in the form of letters.
5. Epistolary evidence is evidence that is in the form of letters.