lucid

[loo-sid]

adjective

1.)   easily understood; completely intelligible or comprehensible:

            a lucid explanation.

2.)   characterized by clear perception or understanding; rational or sane:

                    a lucid moment in his madness.

3.)   luminous, glowing, shining or bright.

4.)   clear, pellucid, transparent, translucent.
 

Origin of lucid

1574-1585,  Latin lūcidus, equivalent to lūc-, stem of lūx light¹+ -idus -id