Aspect-oriented programming

Concern : A concern is a particular set of behaviors needed by a computer program, the conceptual sections. A concern can be as general as database interaction or as specific as performing a calculation, depending on the level of conversation between developers and the program being discussed.

Aspect : An aspect of a program is a feature linked to many other parts of the program, but which is not related to the program's primary function. An aspect cross-cuts the program's core concerns, therefore violating its separation of concerns that tries to encapsulate unrelated functions. For example, logging code can cross-cut many modules, yet the aspect of logging should be separate from the functional concerns of the module it cross-cuts. Isolating such aspects as logging and persistence from business logic is the aim of aspect-oriented software development (AOSD), of which the aspect-oriented programming (AOP) paradigm is the most widely employed

Cross-cutting concern : In computer science, cross-cutting concerns are aspects of a program which affect other concerns. These concerns often cannot be cleanly decomposed from the rest of the system in both the design and implementation, and can result in either scattering (code duplication), tangling (significant dependencies between systems), or both.
For instance, if writing an application for handling medical records, the bookkeeping and indexing of such records is a core concern, while logging a history of changes to the record database or user database, or an authentication system, would be cross-cutting concerns since they touch more parts of the program.

AOP: In computing, aspect-oriented programming (AOP) is a programming paradigm which aims to increase modularity by allowing the separation of cross-cutting concerns. AOP forms a basis for aspect-oriented software development.
AOP includes programming methods and tools that support the modularization of concerns at the level of the source code, while "aspect-oriented software development" refers to a whole engineering discipline.