Terminology

• Should You Write “Nonzero” or “Non-Zero” in Mathematics?
  Both “nonzero” and “non-zero” are accepted spellings; choose one style, use it consistently, and make clear which number system is meant.
• Density vs. Mass Density: What Is the Difference?
  Density usually means mass per unit volume in basic physics, but the term also applies to other quantities; context and units clarify which one.
• Can Magnitude Be Negative?
  Magnitude is never negative: it measures size. Signed quantities such as potential energy or a vector component can be negative, depending on direction or reference.