Secondarily, a science is expressed in words and written down in text books. Geometry is the paradigm of a science.
Science is a sub-set of knowledge.
The principles upon which demonstrations or proofs are based are themselves unproven. Some of these, the most general, are immediately known to be true once the terms are understood. There is another kind of habit of knowledge, wisdom, which is the grasp of things in their first principles. I hope this helps.