Specialisation, (orspecialization) is an important way to generate propositional knowledge, by applying general knowledge, such as the theory of gravity, to specific instances, such as "when I release this apple, it will fall to the floor". Specialisation is the opposite of generalisation.
Concept B is a specialisation of concept A if and only if:
every instance of concept B is also an instance of concept A; and
there are instances of concept A which are not instances of concept B.