Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Para- \Par"a-\ [Gr. para` beside; prob. akin to E. for- in forgive. Cf. For-.]
A prefix signifying alongside of, beside, beyond, against, amiss; as parable, literally, a placing beside; paradox, that which is contrary to opinion; parachronism.
(Chem.) A prefix denoting:
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.
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.
Douglas Harper's Etymology Dictionary
before vowels, par-, word-forming element meaning "alongside, beyond; altered; contrary; irregular, abnormal," from Greek para- from para (prep.) "beside, near, issuing from, against, contrary to," from PIE *prea, from root *per- (1) "forward, through" (see per). Cognate with Old English for- "off, away."
word-forming element meaning "defense, protection against; that which protects from," from Italian para, imperative of parare "to ward off," from Latin parare "make ready" (see pare).
Etymology 1 pre. 1 above, beyond 2 beside, near, alongside 3 abnormal, incorrect 4 resembling 5 (context chemistry English) In isomeric benzene derivatives, having the two substituents in opposite positions (compare ortho- and meta-.) Etymology 2
pre. (context obsolete not productive English) to guard against, to avert, to shield from; to provide protection against, defence from Etymology 3
pre. Forming words relating to activities carried out with a parachute.