x_{1} is a mereological object which underlaps with mereological object x_{2} via at least object x_{3} in universe of discourse x_{4}.

There exists an object y in x_{4} such that x_{1} is a part of y, and x_{2} is a part of y; moreover, x_{3} is such a y (but others may exist). Sometimes, this definition is restricted so that objects such that all things in the universe are part(s) of them are not candidates for y. See also: "pagbrkuclapi", "pagbu".

- pagbrkuclapi
- x
_{1}is a mereological object which overlaps with mereological object x_{2}via at least object x_{3}in universe of discourse x_{4}.