collateral, synchronous, synchronic, synchronal, analog, analogue, collimate, duplicate, twin, latitude, more...

perpendicular, intersecting, skew, convergent, divergent

parallel lines, parallel circuits, parallel processing, parallel computing, parallel parking, parallel universe, parallel bars, parallel structure, more...

38th, close, interesting, exact, striking, 49th, second, ninth, eighth, obvious, straight

on the same level,   at the same level,   similar situation,   same side,   similar experience,   like some lines,   same direction,   in tangent,   lined up with,   same situation