Internal

a.
  1. Inward; interior; being within any limit or surface; inclosed; -- opposed to external; as, the internal parts of a body, or of the earth.
  2. Derived from, or dependent on, the thing itself; inherent; as, the internal evidence of the divine origin of the Scriptures.
  3. Pertaining to its own affairs or interests; especially, (said of a country) domestic, as opposed to foreign; as, internal trade; internal troubles or war.
  4. Pertaining to the inner being or the heart; spiritual.
  5. Intrinsic; inherent; real.
  6. (Anat.) Lying toward the mesial plane; mesial.
    7. Internal angle (Geom.),
    an interior angle. See under Interior.
    Internal gear (Mach.),
    a gear in which the teeth project inward from the rim instead of outward.