The term "letter" can refer to:

• Letter, a written message from one party to another.
• Letter, a character of an alphabet, abjad, or syllabary.
• Letter, a standard paper size used primarily in the United States.
• Letter, an award in the form a high school's or college's initial given for excellent achievement, usually in athletics.
• Letters can also mean literature, as in arts and letters.
• Letters is also the name of several editions of collections of letters by famous people (sometimes also by fictional people), for example:
  • Letters ascribed to Plato: see Letters (Plato)