As an atheist, I have truly grown to hate the title. Not because it holds ridiculous negative connotations, or because it is a title that is completely misunderstood, but because it legitimately says nothing. People define themselves by what they believe, not by what they reject (how many people do you hear calling themselves non-liberals or non-soccer players). Many people (atheists included) make the mistake of thinking that atheism is the belief that NO GOD exists. This is incorrect for about 99% of all non-believers. What most atheists really do is REJECT the claim that a deity exists. I understand that this seems like nothing but semantics; however, the distinction is important in order to truly understand what an atheist is.
To claim that there is no god is a faith-based position that I personally find as stupid as claiming that there is one. There is absolutely no testable way to prove that god does not exist and almost no one argues this point. There is no way to prove a negative, making such a claim unfalsifiable. However, no intelligent atheist will ever claim that there is no god (doing so is often referred to gnostic atheism or “hard atheism”). Most atheists will reject the claim that there is a god based on insufficient evidence (what is known as agnostic atheism or “soft atheism”). It is very important to understand the difference between asserting a negative (stupid in almost every case because a negative cannot by definition be verified) and rejecting a positive claim. What this means in simpler terms is that most atheists do not necessarily claim that there is no god (although most will say that they do out of simplicity); they believe that there is no good reason to assume god exists. Again, this is an important distinction because claiming that no god exists is a faith-based claim; it is totally and completely unverifiable under any empirical experiment.
I have recently become aware that many believers consider atheism to be a religion of nonbelief. This claim is of course ridiculous (unless the term religion is defined so loosely that it loses all actual meaning and comes to include every form of ideology). Not playing football is not a sport, not collecting stamps is not a hobby, and not accepting a faith-based assertion is not a religion. Only hard atheism may be considered a religion, because it is a faith claim, as opposed to soft atheism, which requires no faith in anything beyond the empirical.
The term atheism really has no meaning except “someone who does not believe that sufficient evidence exists in order to make the claim that god exists”. I am sure that many people will jump in arms after reading this and claim that what I am actually describing is an agnostic, and to a degree they would be correct. Colloquially, an agnostic is a fence-sitter of sorts. It is used to describe someone who claims that they are unsure if there is sufficient evidence to accept the claim that god exists. However, the true definition of an agnostic is someone who does not know, whereas the true definition of an atheist is someone who rejects theism (and for simplicity we also say they reject deism). Atheism and agnosticism refer to two different ideas: beliefs and knowledge. To be an agnostic atheist is to be someone who does not know whether god does exist, but believes that there is no reason to assume that a god exists, whereas a gnostic atheist would be someone who claims that they know (or almost certainly know) that god does not exist (and believes that there is evidence to support such a claim). Similarly, an agnostic theist would be someone who believes that god exists but does not know that sufficient evidence to make a claim either way exists, and a gnostic theist claims that they know (or almost certainly know) that god exists (and believes that there is evidence to support that claim).
Both gnostic theist and atheism present the same problem, which is belief without sufficient evidence (I am of course assuming that there is not sufficient evidence to adequately prove god’s existence, because that is not the point of this article). Agnostic theism provides a problem because the default position for any unknown claim of significance should be skepticism. For example, if someone told me that I would marry Scarlett Johansson, it would incredible foolish of me to live my life thinking that I will marry a millionaire until I was shown sufficient evidences (such as a wedding contract, or I actually talked to Mrs. Johansson). So unless evidence exists to make a gnostic claim, it makes no sense to believe such a claim to be true so long as the belief actually has some bearing. For example I might believe my friend if he told me that his brother had green eyes without fact checking, because such a belief has little bearing on my life.
So overall, atheism is a title based on the rejection of a deity, NOT the claim that such a deity does not exist (this excludes gnostic atheists, but I believe most atheists to be agnostic atheists, so I am generalizing). Atheists therefore do not possess faith (defined as belief without empirical evidence). Atheism is therefore not a religion in any strict sense of the term. It is not a lifestyle or an ideology. It is nothing more than title given to those who reject a claim.