"parallel lines never converge"; "concentric circles are parallel"; "dancers in two parallel rows"
is similar to
(especially of vectors) parallel but oppositely directed
"antiparallel vectors"
is similar to
situated or running side by side
"collateral ridges of mountains"
is similar to
(of lines, planes, or surfaces) never meeting or crossing
see also
able to be compared or worthy of comparison
see also
having similarity in size, shape, and relative position of corresponding parts