Absorption is a valid argument form and rule of inference of propositional logic.

The rule makes it possible to introduce conjunctions to proofs.

It is called the law of absorption because the term

The absorption rule may be expressed as a sequent: where

is a metalogical symbol meaning that

in some logical system; and expressed as a truth-functional tautology or theorem of propositional logic.

The principle was stated as a theorem of propositional logic by Russell and Whitehead in Principia Mathematica as: where

are propositions expressed in some formal system.

If it will rain, then I will wear my coat.