# Definition:Right Angle/Perpendicular/Plane

< Definition:Right Angle | Perpendicular(Redirected from Definition:Line Perpendicular to Plane)

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## Definition

In the words of Euclid:

*A***straight line**is**at right angles to a plane**when it makes right angles with all the straight lines which meet it and are in the plane.

(*The Elements*: Book $\text{XI}$: Definition $3$)

In the above diagram, the line $AB$ has been constructed so as to be a **perpendicular** to the plane containing the straight lines $CD$ and $EF$.