Design Patterns
A reusable solution to a recurring problem. [Design] patterns try to
capture the common invariant properties of the problem and the
essential relationships needed to solve the problem. (...) They are
abstract solutions that allow a designer to reuse ideas that worked in
the past for commonly faced problems.
Ontology
A specification of a conceptualization. That is, an ontology is a
description of the concepts and relationships that exist within a
certain domain.