What is Reductionism and unification?

Reductionismare identical to, or are collections or combinations of, entities of another (often simpler or more basic) kind or that expressions denoting such entities are definable in terms of expressions denoting other entities. Thus, the ideas that physical bodies are collections of atoms or that a given mental state (e.g., one person’s belief that snow is white) is identical to a particular physical state (the firing of certain neurons in that person’s brain) are examples of reductionism.

Unification: It is the act of unifying the different laws valid for different phenomena in to a single theory that explains all the different phenomena. Eg. ... These are unified under theory of electromagnetism; Reduction: It is the effort to solve a complex problem by breaking it into simpler parts.