Child abuse means that a parent or step-parent injures a child on purpose, time after time. If a brother or sister or someone else in the house injures a child on purpose, and the parent doesn't protect the child, that is also abuse. Abuse is not the same s discipline.
Some parents discipline by spanking.
That is not abuse. Discipline helps us learn what to do and what not to do. Abuse makes us feel terrible about ourselves. Another kind of abuse is sexual abuse . That is when an adult or older teenager tricks or forces a child into some kind of sex.