A declarative sentence that is either true or false, but not both, is a proposition.

Also known as a statement.

Usually denoted using lowercase letters pp, qq, rr, ss or tt.

These sentences would be considered propositions:

  • It is Monday today.
  • I am 14 years old.
  • 1 + 1 = 3

The truthfulnes or falsity of a proposition is called its Truth Value. Denoted by TT or FF, or 1 and 0 in computer science.