Lattices are partially ordered sets such that a least upper bound and a greatest lower bound can be found for any subset consisting two elements. Lattice theory is an important subfield of order theory.

Lattices are partially ordered sets such that for any two elements $x$, $y$ there is a supremum $x\vee y$ and infimum $x\wedge y$ of the set $\{x,y\}$. Lattice theory is an important subfield of order theory.

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