- Approximation errors(as used in physics and mathematics)
- The differences between a simplified or estimated version of something and what it actually is in reality.
- Areal law(as used in physics and astronomy)
- A principle stating that a planet sweeps out equal areas in equal times as it orbits the sun (also called Kepler's second law).
- Biconditional(in formal logic)
- A logical statement that says two things are true if and only if each other is true; it's a two-way relationship (like saying 'you can vote if and only if you're 18').
- Derivable(in logic)
- Able to be proven or worked out step-by-step using the formal rules of a logical system.
- Empirical commitment(as used in philosophy of science)
- A claim about how the real world actually works, based on observation and experiment rather than pure reasoning.
- Generalization(Used in SQML proofs involving quantifiers)
- A proof rule in SQML by which a universally quantified formula is derived from an open formula, e.g. deriving ∀x(Fx → Fx) from the tautology Fx → Fx
- Presupposes(as describing what Plantinga's argument takes for granted)
- Assumes something to be true without proving it—like how an argument might presuppose that logic works, without first arguing that logic is valid.
- Props. (Propositions)(as used in mathematical and philosophical texts)
- A shorthand reference to earlier statements or theorems being discussed—'Props. 1–2' means 'Propositions 1 and 2.'
- Scale proportionally(as used in mathematics and physics)
- Change in a way that maintains the same ratio or relationship—if one thing doubles, the other doubles too.
- centripetal force(Book 1, Propositions 1 and 2)
- A force directed toward a fixed center that governs orbital motion; Newton's framework requires purely centripetal forces to produce the equal-areas property
- quam proxime(Newton uses quam proxime forms of exact propositions to apply idealized mathematical results to real physical observations that only approximately satisfy the exact conditions)
- A Latin phrase meaning 'as nearly as possible' or 'approximately'; used by Newton to denote that a proposition holds in an approximate or limiting sense rather than exactly