A formal theory is said to be incomplete if it contains fewer theorems than would be possible while still retaining consistency.
Incompleteness
See also
Consistency, Gödel's First Incompleteness Theorem, Gödel's Second Incompleteness TheoremExplore with Wolfram|Alpha
References
Chaitin, G. J. "G. J. Chaitin's Home Page." http://www.cs.auckland.ac.nz/CDMTCS/chaitin/.Referenced on Wolfram|Alpha
IncompletenessCite this as:
Weisstein, Eric W. "Incompleteness." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Incompleteness.html