Well, there's strong and weak atheism. Strong atheism being the position akin to "I know there is no god". Agnosticism would be the belief that you cannot draw a conclusion, that the evidence is inconclusive, or that knowledge is impossible. Weak atheism would be the position akin to "there's no reason to believe, so I don't".
To flog a well beaten analogy: the teapot in orbit around the sun directly opposite the earth.
The theist says there's definitely a teapot. The strong atheist says there definitely isn't. The agnostic withholds judgement because we cannot know. The weak atheist says there's no reason to believe there's a teapot.
"Lack of belief" is specifically an atheist trait. Agnosticism is lack of knowing on the matter.
Atheism and agnosticism are compatible, which is why there's often conflation between the two. I personally don't think we can know, but I see no reason to believe.
There are also agnostics who believe in a deity, even though they don't think we can really know.
Finally, for the last bit of pedantry: empirical evidence isn't the only type of knowledge. Math, for example, is not evidence based, nor is it empirical. We don't typically count algebra as a matter of faith however.
There are schools of atheism that would claim that you can know that God does not exist because said existence is logically contradictory in a way that can be deductively demonstrated, similar to how things can be disproven in mathematics.