Axiom

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In the book Elements of Euclid twenty-three definitions are described.

1.	A point is that which has no part.
2.	A line is a breadthless length ...
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8.	A plane angle is the inclination to one another of two lines in a plane which meet one another and do not lie in a straight line.
9.	And when the lines containing the angle are straight, the angle is called rectilineal.
10.	When a straight line set upon a straight line makes the adjacent angles equal to one another, each of the equal angles is called right, and the straight line standing on the other is called perpendicular to that on which it stands.
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23.	Parallel straight lines are straight lines which being in the same plane and being produced indefinitely in both directions, do not meet one another in either direction.

The most influential book in the history of mathematics, called Elements, was compiled by the Greek Euclid in 300 BC.