What is a point?
What are lines?
Breadthless length.
What is a line?
That all right angles...
...are equal to one another.
The whole is...
...greater than the part.
Figures which are contained by straight lines.
What are rectilineal figures?
A plane figure contained by one line such that all the straight lines falling upon it from one point among those lying within the figure are equal to one another.
What is a circle?
That which has length and breadth only.
To describe a circle...
...with any center and distance.
If equals be subtracted from equals...
...the remainders are equal.
A line which lies evenly with the points on itself.
What is a straight line?
That which is contained by any boundary or boundaries.
What is a figure?
A quadrilateral which is both equilateral and right-angled.
What is a square?
To draw a straight line...
...from any point to any point.
Things which are equal to the same thing...
...are also equal to one another.
Any straight line drawn through the center and terminated in both directions by the circumference of the circle.
What is a circumference?
The inclination to one another of two lines in a plane which meet one another and do not lie in a straight line.
What is a plane angle?
A rectilineal figure contained by three lines.
What is a trilateral figure?
To produce a finite straight line...
...continuously in a straight line.
If equals be added to equals...
...the wholes are equal.
A quadrilateral figure which has its opposite sides and angles equal to one another, but is neither equilateral nor right-angled.
What is a rhomboid?
A quadrilateral figure which is equilateral but not right-angled.
What is a rhombus?
Straight lines which, being in the same plane and being produced indefinitely in both directions, do not meet one another in either direction.
What are parallel lines?
That, if a straight line falling on two straight lines makes the interior angles on the same side less than two right angles...
...the two straight lines, if produced indefinitely, meet on that side on which are the angles less than the two right angles.
Things which coincide with one another...
...are equal to one another.