In a geometry, points are said to be collinear if they all lie on a straight line.
In the following picture, , , and are collinear.
{$P$} \rput[a](3,-0.3){$B$} \rput[a](0,0.03){.} \end{pspicture}](http://images.planetmath.org:8080/cache/objects/2281/l2h/img4.png "\begin{pspicture}(-2,-0.3)(3,0.1) \psline(-2,0)(3,0) \psdots(-2,0)(0,0)(3,0) \rp... ... \rput[a](0,-0.3){$P$} \rput[a](3,-0.3){$B$} \rput[a](0,0.03){.} \end{pspicture}"){kind=small}