In the branch of linguistics known as pragmatics, a presupposition (or ps) is an implicit assumption about the world or background belief relating to an utterance whose truth is taken for granted in discourse. Examples of presuppositions include:

• Jane no longer writes fiction.
  • Presupposition: Jane once wrote fiction.
• Have you stopped eating meat?
  • Presupposition: you had once eaten meat.
• Have you talked to Hans?
  • Presupposition: Hans exists.