Rule of three

Rule of three or Rule of Thirds may refer to:

Science and technology

Rule of three (aeronautics), a rule of descent in aviation
Rule of three (C++ programming), a rule of thumb about class method definitions
Rule of three (computer programming), a rule of thumb about code refactoring
Rule of three (hematology), a rule of thumb to check if blood count results are correct
Rule of three (mathematics), a method in arithmetic
Rule of three (medicinal chemistry), a rule of thumb for lead-like compounds
Rule of three (statistics), for calculating a confidence limit when no events have been observed
Rule of threes (survival), the rule of threes involves the priorities in order to survive

Rule of Three, a podcast by Jason Hazeley and Joel Morris
Rule of Three, a series of one-act plays by Agatha Christie
The Bellman's Rule of Three in The Hunting of the Snark, a poem by Lewis Carroll
The Rule of Thirds, a 2008 album by Death In June