• Physical abuse is often the most easily spotted form of abuse. It may be any kind of hitting, shaking, burning, pinching, biting, choking, throwing, beating, and other actions that cause physical injury, leave marks, or produce significant physical pain.
• Sexual abuse is any type of sexual contact between an adult and anyone 18 or younger, or between a significantly older child and a younger child. If a family member sexually abuses another family member, this is called incest.
• Emotional abuse can be difficult to pin down because there may not be physical signs. Emotional abuse happens when yelling and anger go too far or when parents constantly criticize, threaten, or dismiss kids or teens until their self-esteem and feelings of self-worth are damaged. Emotional abuse can hurt and cause damage just as physical abuse does.
• Neglect is probably the hardest type of abuse to define. Neglect occurs when a child or teen doesn't have adequate food, housing, clothes, medical care, or supervision. Emotional neglect happens when a parent doesn't provide enough emotional support or deliberately and consistently pays very little or no attention to a child. But it's not neglect if a parent doesn't give a kid something he or she wants, like a new computer or a cell phone.

-taken from: http://www.kidshealth.org/teen/your_mind/families/family_abuse.html