It's an interesting question. Discipline is intended to teach children, which is ultimately intended for the child's well being. Abuse is mistreatment, treatment that harms the child. The problem comes in when a parent abuses a child, thinking it's in the child's best interest, that it will teach them something. So it's not a clearly defined thing actually. Some have put the line at whether or not a bruise is left on the child, which makes spanking OK. But some view spanking as a form of abuse, they see any form of physical discipline as abuse. On either extreme, it's fairly clear what is child abuse and what is disciple, but there is unfortunately a fuzzy middle ground. You can abuse a child a never touch them. In fact, you can abuse a child BY never touching them (neglect, emotional abuse, etc). It would be wonderful if it were more clear cut.

abuse is when you deliberately hit ur child because you are meerly evil. but discipline is teaching manners and good habits through seriousness and sternnnesss lol. weellll thats my opinion