dialogue [ME] This comes via Old French and Latin from Greek dialogos, from dialegesthai ‘converse with, speak alternately’: the formative elements are dia- ‘through, across’ and legein ‘speak’. The tendency in English is to confine the sense to a conversation between two people, perhaps by associating the prefix dia- with di-. Dia- is also found in diameter [LME] ‘the measure across’; diaphanous [E17th] ‘shows through’; diaphragm [LME] a barrier that is literally a ‘fence through’, and diaspora [L17th] a scattering across, literally ‘a dispersion’.