Definitions Flashcards
Line
A line is breadthless length.
Point
A point is that which has no part
Straight Line
A Straight Line is a line which lies evenly with the points on itself.
Surface
A Surface is that which has length and and breadth only (the extremities of a surface are lines).
Plane Surface
A Plane Surface is a surface which lies evenly with the straight lines on itself.
Plane Angle
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.
Rectilineal
When lines containing an angle are straight.
Perpendicular
When a straight line set up on a straight line makes the adjacent angles equal to one another, and each of the equal angles is right, the straight line standing on the other is called a perpendicular to that on which it stands.
Obtuse Angle
An Obtuse Angle is an angle greater than a right angle.
Acute Angle
An Acute Angle is an angle less than a right angle.
Boundary
A Boundary is that which is an extremity of anything.
Figure
A figure is that which is contained by any boundary or boundaries.
Circle
A Circle is 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.
Center of a Circle
Point
Diameter of a Circle
Any Straight Line drawn through the center and terminated in both directions by the circumference of the circle, and also bisects a circle.
Semicircle
The figure contained by the diameter and the circumference cut off by it. The center of the semicircle is the same as that of the circle.
Rectilineal figures
Those figures contained by Straight Lines.
Trilateral Figures
Figures contained by three Straight Lines.
Quadrilateral Figures
Figures contained by four Straight Lines.
Multilateral Figures
Figures contained by more than four Straight Lines.
Equilateral Triangle
Trilateral trilateral figure with three equal sides.
Isosceles Triangle
Trilateral figure that has two sides alone equal.
Scalene Triangle
Trilateral figure which has three sides unequal.
Right-Angled Triangle
Triangle which has a right angle.
Obtuse-Angled Triangle
Triangle which has an obtuse angle.
Acute-Angled Triangle
Triangle which has three angles acute.
Square
Quadrilateral figure that which is both equilateral and right-angled.
Oblong
Quadrilateral figure that which is right-angled but not equilateral.
Rhombus
Quadrilateral figure that which is equilateral but not right-angled.
Rhomboid
Quadrilateral figure that which has its opposite sides and angles equal to one another but is neither equilateral nor right-angled.
Trapezia
Quadrilaterals that are not square, oblong, rhombus or rhomboid.
Parallel Straight Lines
Straight lines which, being in the same plane and being produced indefinitely in both directions, do not meet one another in either direction.
