Constitutive equationLaws of scienceDefining equation (physical chemistry)Defining equation (physics)List of equations in classical mechanicsTable of thermodynamic equationsList of equations in wave t ...
Main article: Double counting (proof technique)Double counting is a technique that equates two expressions that count the size of a set in two ways.Pigeonhole principleMain article: Pigeonhole princip ...
Main article: Inclusion-exclusion principleThe inclusion-exclusion principle relates the size of the union of multiple sets, the size of each set, and the size of each possible intersection of the set ...
Main article: Rule of productThe rule of product is another intuitive principle stating that if there are a ways to do something and b ways to do another thing, then there are a · b ways to do both t ...
Main article: Rule of sumThe rule of sum is an intuitive principle stating that if there are a possible outcomes for an event (or ways to do something) and b possible outcomes for another event (or wa ...
In proving results in combinatorics several useful combinatorial rules or combinatorial principles are commonly recognized and used.The rule of sum, rule of product, and inclusion-exclusion principle ...
