[adj] (of language) transparently clear; easily understandable; "writes in a limpid style"; "lucid directions"; "a luculent oration"- Robert Burton; "pellucid prose"; "a crystal clear explanation"; "a perspicuous argument"
[adj] transmitting light; able to be seen through with clarity; "the cold crystalline water of melted snow"; "crystal clear skies"; "could see the sand on the bottom of the limpid pool"; "lucid air"; "a pellucid brook"; "transparent cristal"
[adj] capable of thinking and expressing yourself in a clear and consistent manner; "a lucid thinker"; "she was more coherent than she had been just after the accident"
[adj] having a clear mind; "a lucid moment in his madness"
clear, coherent, crystal clear, crystalline, limpid, logical, luculent, pellucid, perspicuous, rational, sane, transparent