A prefix denoting: (a) Likeness, similarity, or connection, or
   that the substance resembles, but is distinct from, that to the name of
   which it is prefixed; as paraldehyde, paraconine, etc.; also, an
   isomeric modification. (b) Specifically: (Organ. Chem.) That two groups
   or radicals substituted in the benzene nucleus are opposite, or in the
   respective positions 1 and 4; 2 and 5; or 3 and 6, as paraxylene;
   paroxybenzoic acid. Cf. Ortho-, and Meta-. Also used adjectively.