<logic> The property of a system by which new wffs can be added to any set of wffs without invalidating previously valid derivations from that set. If A is any wff, and G and D any sets of wffs, a system is monotonic iff G |- A => D , G |- A. In non-monotonic logics derivations can be invalidated when the set of premises is enlarged.
[Glossary of First-Order Logic]
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