A priori
Etymology
Latin for “from the earlier,” paired with its opposite “a posteriori,” “from the later.” The distinction was sharpened by Kant, for whom “7 + 5 = 12” is knowable a priori, while “the water is cold” is a posteriori, known only through the senses.
adjective · /ah pree-OR-ee/
Known or reasoned independently of experience, from principles alone rather than from observation.
What it names
The kind of knowledge you can establish just by thinking — like a mathematical truth — as opposed to what you must go and check.
Example
That all bachelors are unmarried is an a priori truth; that the café is closed on Mondays is something you learn a posteriori.
Related idea
A priori knowledge needs no observation, whereas empirical knowledge rests entirely on it; the pair maps roughly onto reasoning by deduction versus by induction.