The two phrases are equivalent: collinear means in the same line [segment].
A line segment (sometimes just segment) is a pair of endpoints and all the points on a line between them.
Yes, a plane containing 2 points of a line contains the entire line. Let us consider two points on a plane and then draw a line segment joining those two points. Since the points lie on the plane so line segment has to lie completely on that plane too. Now if we extend the line segment indefinitely in both directions we get a line and that line also has to lie on the same plane since some definite part(line segment) of it(line) also lies on the same plane.
A chord is a line segment whose endpoints lie on a circle. A secant is a line (or line segment) that intersects a circle in two places, endpoints NOT on the circle.
Collinear lines lie on the same straight line
the endpoints lie on each other
The centroid, circumcenter and orthocenter are the 3 points of concurrency that always lie on a line.
The same line.
lines which lie in same pane are known as parallel lines or lines which do not intersect are known as parallel lines they extend in both the direction