Parallel

A parallel ( from the Greek para " beside" and allelon " one another" ) is:

• In the geometry of one of two lines lying in a plane and do not intersect each other, see parallelism ( geometry)
• A similarity in the behavior or facts ( " historical parallel " )
• In music, a shift in the pitch, see Parallel (Music)
• Especially in music theory, a relationship between keys, see the relative key
• Also in music theory, a relationship between triads, see Parallel Sound