For instance, the summing of numbers or the concatenation of strings or other sequences are operations that can logically apply to any number of operands.
The natural interpretation of is negation; that of concatenation is any connective that, when combined with negation, forms a functionally complete set of connectives.
For instance, the context-free languages are known to be closed under union, concatenation, and intersection with regular languages, but not closed under intersection or complement.