Ambrosius Theodosius Macrobius, from Commentary on the Somnium Scipionis: (4th Century C.E.)

All dreams may be classified under five main types: there is the enigmatic dream, in Greek oneiros; second, there is the prophetic vision, in Greek horama; third, there is the oracular dream, in Greek chrematismos; fourth, there is the nightmare, in Greek enhypnion; and last, the apparition, in Greek, phantasma, which Cicero, when he has occasion to use the word, calls "visum." Nightmares may be caused by physical or mental distress, or anxiety about the future; the patient experiences in dreams vexations similar to those that disturb him during the day. We call a dream oracular in which a parent, or a pious or revered man, or a priest, or even a god clearly reveals what will or will not transpire... We call a dream a prophetic vision if it actually comes true... By an enigmatic dream we mean one that conceals with strange shapes and veils with ambiguity the true meaning of the information being offered, and requires an interpretation for its understanding.