They will understand from the tone of your voice and feel that is your perfect answer to their question and go away satisfied with your answer. They also, as they grow, will experience it by hearing about death in the news and at school by people taking about it. When they are older will know then that it is permanent and part of the life process. Some children will have a harder time than others understanding why and sometimes when this happens, children need counseling to talk about it. When children can get it out and talk about it, somehow it makes the pain easier to accept.
People like to say that every child is the same.
This might be true for child-like actions, but not true when it comes to the way they accept things and events in their life. If you find your child starting to neglect schoolwork, getting into arguments with anyone for no reason all of a sudden, and other strange behavior not normal of this child, you might want to have him or her checked for signs of depression and have them talk to someone outside the family, such as a school counselor or Professional psychiatrist. A professional will know what signs to look for and can offer your child the best program for wellness. Don't expect a speedy recovery or quick answers for the reason your child feels the way they do. Only your child can heal him or herself by themselves and sometimes this can be a long healing process.