It's time to correct this ignorant state of affairs in the mystery world. A cozy must include at least one cat. The murder is usually a domestic crime. The sleuth is almost always an amateur. It's much cozier for a pink-haired elderly lady to point her knitting needle at the murderer than to have the villain collared by the cops and read his Miranda rights.
Graphic violence is eschewed in cozies.
Nobody in cozies has ever seen blood before. The murder weapon in cozies is usually a blunt instrument, i.e., a lapis lazuli paperweight, a fireplace poker, or Larry King. Poison is allowable as the agent of death in cozies but only if death is instantaneous. The ban on vomiting, I think, is in deference to the cat. The language of cozies does not permit the use of four-letter words.