Noah Webster's New International Dictionary of the English Language

1. (a.) Inward; interior; being within any limit or surface; enclosed; -- opposed to external; as, the internal parts of a body, or of the earth.

2. (a.) Derived from, or dependent on, the thing itself; inherent; as, the internal evidence of the divine origin of the Scriptures.

3. (a.) 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. (a.) Pertaining to the inner being or the heart; spiritual.

5. (a.) Intrinsic; inherent; real.

6. (a.) Lying toward the medial plane; medial.