- 1. Prefix denoting a departure from the normal. 2. Prefix denoting involvement of two like parts or a pair. 3. Prefix denoting adjacent, alongside, near, etc. 4. (p-) In chemistry, an italicized prefix denoting two substitutions in the benzene ring arranged symmetrically, i.e., linked to opposite carbon atoms in the ring. For words beginning with p. or p-, see the specific name. [G. alongside of, near]
* * *para- .par-ə, 'par-ə or par- prefix1) closely related to <paraldehyde>2) involving substitution at or characterized by two opposite positions in the benzene ring that are separated by two carbon atoms <paradichlorobenzene> abbr. p- compare META- (2), ORTH- (2)
* * *prefix denoting1. beside or close to. Example: paranasal (near the nasal cavity).2. resembling. Example: paradysentery (a mild form of dysentery).3. abnormal. Example: paralalia (abnormal speech).
* * *symbol p-; in organic chemistry, a prefix indicating a 1,4-substituted benzene ring, e.g., p-xylene (1,4-dimethylbenzene) or p-nitrophenol (4-nitrophenol).
Two examples of disubstituted benzene derivatives with substituents in the para- position. (A), p-xylene (1,4-dimethylbenzene); (B), p-nitrophenol.
Medical dictionary. 2011.