Definition 10.148.1. Let R \to S be a ring map. We say S is formally unramified over R if for every commutative solid diagram
\xymatrix{ S \ar[r] \ar@{-->}[rd] & A/I \\ R \ar[r] \ar[u] & A \ar[u] }
where I \subset A is an ideal of square zero, there exists at most one dotted arrow making the diagram commute.
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