1. Mail that includes letters and postcards and packages sealed against inspection
   - first class, first-class mail, 1st-class mail

Type of: mail

• theorise
• theoriser
• theorist
• theorization
• theorize
• theorizer
• theory
• theory of dissociation
• theory of electrolytic dissociation
• theory of evolution
• theory of games
• theory of gravitation
• theory of gravity
• theory of indicators
• theory of inheritance
• theory of organic evolution
• theory of preformation
• theory of probability
• theory of punctuated equilibrium
• theory of relativity
• theory-based
• theosophical
• theosophism
• theosophist
• theosophy