letter (written character) / letter (written message) / the literal meaning, the plain meaning of something

newsletter

love letter

open letter

letter of intent (legal document outlining one or more agreements between two or more parties before the actual agreements are finalized)

suicide note (message, usually a written note, left by someone who later attempts or commits suicide, usually explaining the reason for the suicide)

(literally, engraving) before lettering, before letters; proof engraving, proof before letters / (figuratively) avant la lettre (before the term was coined)

(engraving) lettered. "Épreuve, gravure après la lettre": a print made after the caption is added (lettered proof)

(engraving) Synonym of après la lettre (lettered)

(historical) lettre de cachet