There were always attempts to classify demons in several categories. Christian demonology accepted that, providing several classifications of the demons.
The first classification was the same that Judaism and other religions had, involving the demons' sexual behaviour (later this simple classification became complex):
But this classification soon became insufficient, and other demonologists suggested different patterns to classify demons. In this way there were classifications based on their nature, the sin with which they tempt humans, the month in which their power was stronger, the saints that were their adversaries, etc. Here follow some examples, listed in chronological order:
There were other classifications, by office, like those written in several grimoires; these are some examples:
See also Hierarchy of the demons.