Conjunction introduction (often abbreviated simply as conjunction and also called and introduction or adjunction) is a valid rule of inference of propositional logic. The rule makes it possible to introduce a conjunction into a logical proof. It is the inference that if the proposition is true. For example, if it is true that "it is raining", and it is true that "the cat is inside", then it is true that "it is raining and the cat is inside". The rule can be stated:

" can be placed on a subsequent line.

Formal notation

The conjunction introduction rule may be written in sequent notation:

are propositions expressed in some formal system is a metalogical symbol is a syntactic consequence are each on lines of a proof in some logical system.

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