prefix
(no longer productive) In verbs: denoting the sense "through", as in perforate.
(no longer productive) In verbs: denoting the sense "thoroughly", as in perfect.
(no longer productive) In verbs: denoting the sense "to destruction", as in pervert.
(no longer productive) In adjectives and adverbs: denoting the sense "extremely", as in perfervid.
(chemistry) Forming nouns and adjectives denoting the maximum proportion of one element in a compound, as in peroxide.
(chemistry) Added to the name of an element in a polyatomic ion to denote the number of atoms of that element (usually four).
prefix
(no longer productive) Denoting the sense "by" or "per", as in perchance or perhaps.