Definition 47.4.1. Let $R$ be a ring. A surjection $P \to M$ of $R$-modules is said to be a projective cover, or sometimes a projective envelope, if $P$ is a projective $R$-module and $P \to M$ is an essential surjection.
Definition 47.4.1. Let $R$ be a ring. A surjection $P \to M$ of $R$-modules is said to be a projective cover, or sometimes a projective envelope, if $P$ is a projective $R$-module and $P \to M$ is an essential surjection.
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