Antithesis (Greek for "setting opposite", from ἀντί "against" and θέσις "placing") is used in writing or speech either as a proposition that contrasts with or reverses some previously mentioned proposition, or when two opposites are introduced together for contrasting effect. This is based on the logical phrase or term. Antithesis can be defined as "a figure of speech involving a seeming contradiction of ideas, words, clauses, or sentences within a balanced grammatical structure. Parallelism of expression serves to emphasize opposition of ideas".