dialectic n.

1570s, "language, speech, mode of speech," especially "form of speech of a region or group, idiom of a locality or class" as distinguished from the general accepted literary language, also "one of a number of related modes of speech regarded as descended from a common origin," from French dialecte, from Latin dialectus "local language, way of speaking, conversation," from Greek dialektos "talk, conversation, speech;" also "the language of a country, dialect," from dialegesthai "converse with each other, discuss, argue," from dia "across, between" (see dia-) + legein "speak" from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')").

1540s, " of or pertaining to logical disputation, relating to the art of reasoning;" see dialectic + -al (1). From 1750 as "of or pertaining to a dialect." From 1788 as "of the nature of philosophical dialectic" (in reference to Kant, later to Hegel and Marx). Related: Dialectally. Dialectical materialism (by 1927) translates Marx's phrase.