Prefix
p-
(obsolete) Scribal abbreviation of pre-.
p-
(organic chemistry) para-
(sports) Initialism of position. (prefixed to a number) (indicates the placing of a competitor in (starting, during, after) a competition)
(chemistry) Initialism of para-. (prefixed as part of a chemical's name) (In isomeric benzene derivatives, having the two substituents in opposite (1,4) positions (compare ortho- and meta-))
Source: en.wiktionary.org