Meaning & History. Possibly from the name of the Greek city of Delphi, the site of an oracle of Apollo, which is possibly related to Greek Î´ÎµÎ»ÏÏÏ (delphys) womb. It was used in the play 'The Prophetess' (1647), in which it belongs to the title prophetess. Popularity. See Popularity Detail.
In elementary geometry, the property of being perpendicular (perpendicularity) is the relationship between two lines which meet at a right angle (90 degrees). The property extends to other related geometric objects. A line is said to be perpendicular to another line if the two lines intersect at a right angle. Explicitly, a first line is perpendicular to a second line if (1) the two lines meet; and (2) at the point of intersection the straight angle on one side of the first line is cut by the second line into two congruent angles.
Line art drawing of parallel lines and curves. In geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. By extension, a line and a plane, or two planes, in three-dimensional Euclidean space that do not share a point are said to be parallel.