Lines

A line can be described as an ideal zero-width,[1] infinitely long, perfectly straight curve (the term curve in mathematics includes “straight curves”)[2] containing an infinite number of points. In Euclidean geometry, exactly one line can be found that passes through any two points. The line provides the shortest connection between the points.[3]

In two dimensions, two different lines can either be parallel, meaning they never meet, or may intersect at one and only one point. In three or more dimensions, lines may also be skew, meaning they don’t meet, but also don’t define a plane. Two distinct planes intersect in at most one line. Three or more points that lie on the same line are called collinear.

Scan from a Kodak 400 Color.