الفهرس 
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Abstract
The thesis consists of five chapters <The first chapter: Introduction
The straight line is the generator of conoids. We start by giving a
further study of the straight line in the three dimensional projective space
p3. Considering the four degrees of freedom of the straight line and using
the LINE GEOMETRY we define.
(i) The line complex if one of the four degrees of freedom is replaced by
one constraint.
(ii) the line congruence if two of the four degrees of freedom are replaced
by two constraints.
(iii) the ruled surface if three of the four degrees of freedom are replaced
by three geometrical constraints.
The third case is the required case 111 which the TIlled surface
may be a conoid. In the case of conoids, the three geometrical constraints
are three [;eometrical directrices. We distinguish between two subcases:
(1) If there are not common points of the three directrices, for example:
right and oblique circular conoids, right helicoids, right and oblique
spherical conoids, hyperbolic paraboloid (as a special case).
(2) IF there are common points of the directrices, for example, Plucker
conoid which is a cubic ruled surface. We held an analogy between p3
and ps
* : p3 ~ ps
Some results on linear complex, linear congruence and ruled
surfaces were obtained. The degree of a ruled surface given by three
geometric directrices is discussed also in this introduction.