What I mean when I say...

"most atheists" or "most theists"

I don't mean "most" in any statistical sense. I simply mean that, in my experience talking to lots of people in person and on the internet over the years, I've noticed trends.

god, God, and gods

Usually when I say "God", I mean the Judeo-Muslim-Christian deity. When I say "god", I mean either a god in the generic sense, or a deity of faiths other than Judaism, Christianity, or Islam (not that I hold any one deity in higher esteem than another, it is an arbitrary choice based on my anticipated readership.

belief in...

When I say "believe in" something or "belief in" something, I mean specifically the belief in the existence of the thing. I don't mean trust or confidence in the thing. For example, when I say "belief in God", I mean belief that God exists. This is different from our "belief in humanity" which means our trust in the goodness of humanity, not our belief that humanity exists.

faith

I use faith in 2 ways. I use it to mean belief in the existence of something (see "belief in" above). I also use it to mean having confidence or trust in something as in "faith in humanity". When I need to distinguish between these two meanings, I use "belief in" (see "belief in" above), "trust", or "confidence" instead.

fundamentalist

This term originated as the result of a 12 volume Christian publication entitled "The Fundamentals: A Testimony To The Truth." But since that publication, the meaning has expended to include any theist who rigidly adheres to religious dogma and is intolerant of conflicting views. I use "fundamentalist" in this broader sense.