Nihil means “nothing.” -ism means “ideology.” But this seems to be self-refuting. To say that this means that someone “believes in nothing” is not really helpful, as believing in something suggests there is something to be believed in, but if that something is nothing, then there is not something to be believed in. 

Therefore, it is easy to fall into the trap of thinking “Everything is nihilism!” which of course leads to thinking “Nothing is nihilism!”

If optimism is hopefulness, then pessimism is hopelessness. Pessimism is dark and depressing. But it is not nihilism.

To be with a pessimist is to know that you are with a pessimist. But you can be with a nihilist and have no idea. Indeed you could yourself be a nihilist and have no idea. Such a lack of awareness is the point of nihilism, as nihilism is all about hiding from despair rather than dwelling on it.

In fact, optimism is more similar to nihilism. If optimism leads us to wait for something good to happen then optimism leads us to do nothing.  

Today, a cynic is someone who looks down on society and sees it as fake, because the cynic sees the people who make up society as fake. He believes that morality is a mere pretense and people act on their own self-interest even when they seem to be helping other people. 

Cynicism, like pessimism, is about negativity. While pessimism is about despair, cynicism is about disdain. Cynics are not nihilists because cynics embrace rather than evade mendacity.

The idealists constructs an alternate reality, a reality of ideas. As the idealist focuses more and more on how reality ought to be, the idealist becomes less and less concerned with how reality is. 

The utopian views of the idealist may be more compelling than the dystopian views of the cynic, but dystopian views are at least focused on this world, whereas utopian views are, by definition, focused on a world that does not exist. 

It is for this reason that to use other-worldly idealism to refute this-worldly cynicism is to engage in nihilism.

To be apathetic is to be without feeling, to be without desire. To be apathetic is to be seen as not caring about anything. The apathetic individual feels nothing. But it is not nihilism. 

Apathy can be an attitude (“I don’t care about that”) or a character trait (“I don’t care about anything”). However, in either case the apathetic individual is expressing a personal feeling and is not making a claim about how everyone should/shouldn't feel.

But the nihilist has feelings. It’s just that what the nihilist has feelings for is itself nothing. This is why a Nihilists cannot have apathy. 

Pity is nihilistic insofar as it allows us to evade reality, by allowing us to feel that we are better than we are and better than those in need. 

The morality of pity drives us to feel pity and to feel good for feeling pity. Having such feelings is worse than feeling nothing. If we feel good when we feel pity, then we are motivated only to help the individuals we feel pity for rather than to help end the systemic injustices that create such pitiful situations in the first place.