What is the meaning of the word "even"?

Definitions:

Equal in number, amount, or value. ADJECTIVE
- The school had an even gender balance among staff and students.
Flat and smooth. ADJECTIVE
- Prepare the site, then lay an even bed of mortar.
Having little variation in quality; regular. ADJECTIVE
- They traveled at an even and leisurely pace.
Make or become even. VERB
- She cut the hair again to even up the ends.
Of a number divisible by two without a remainder. ADJECTIVE
- A meter that reads only in even numbers.
Of a person's temper or disposition, equable; calm. ADJECTIVE
- He was a man of good humor and even temper.
Of two people, in a state of being equal with each other, having eliminated and imbalance or debt. ADJECTIVE
- Just one more favor and we're even, Ok?
Used in comparison for emphasis. ADVERB
- He knows even less about it than I do.
Used to emphasize something surprising or extreme. ADVERB
- They have never even heard of the US.