“and” intersects two selections (logical set-wise AND).

selection and selection

resi 10-40 and name ca

Natural confusion arises from the use of “and” versus “or”, since in English, we use “and” in terms of bringing things together (“I want X and Y and Z.”). When dealing with atomic sets, one must use the set-wise “or” in place of the English “and” in order to express aggregation (“I want all atoms in sets X or Y or Z”).

not | or

Selections