What is happiness?
Happiness is defined in many ways. There are the dictionary meanings. But delve deeper.. and what do you get?
You get all sorts of different meanings that pop into your brain. For example, a terrorist would find joy in destroying an economically-related (and very important) building. A businessman would not, as that would mean that stocks and shares would be affected, they would probably plunge. This would make the businessman distressed. The terrorist would be happy, but not the businessman.

So, there you have it. Happiness is not a general term. It is specific. It is like a suffix or prefix - they don't make sense until you combine them with another word.

Let's relate to a simpler kind of Happiness, yet quite complex.
The Happiness of living under a roof, eating the minimal amount to stay alive, being able to crap even... These are some kinds of Happiness that though simple, are actually quite complex. Complex in the sense that they may seem very difficult to achieve by the standards of poorer people.

Though Happiness is specific, that is only when pertaining to the audience. It is, however, general, when referring to the feeling you get when you feel Happiness. Easily said, you feel "happy". But sometimes, it is at the expense of others.