All three words are very similar. People rarely use the word "maltreat" in speech, but you may see it in writing sometimes. "Maltreat" is pretty much the same as "mistreat." "Abuse" and "mistreat" are also similar, but "abuse" is stronger. If you say that a mother "mistreats" her son, it means that she does not treat him well. She might be mistreating him in a mild way or in a severe way -- it's not clear. If you say that she "abuses" her son, it sounds like she physically hits him, or says very cruel things to him. Usually, if you "abuse" someone, it isn't mild. In most cases, all of these words can be used interchangeably, but the word "abuse" creates a stronger mental image of severe mistreatment.

As a non teacher native, I can just tell you that "abuse " is much more serious sounding than " mistreat " Although technically the same, , we use abuse to mean more severe mistreatment.

"Abuse" is stronger than "mistreat". They can be interchanged, but generally if you say "He abuses his pet", that suggests that the mistreatment or unkind treatment of the animal is greater than if "he mistreats his pet". Maltreat is only rarely used in this context where I am. You would choose between "mistreat" or abuse".

I agree with the nice woman who already helped you. Now I can edit your question! “mistreat”“abuse”“maltreat”，Is there any difference between these three words? I looked these up in the dictionary and they all are about treating a person or an animal in a cruel, unkind or unfair way. What's the difference for usage in a sentence?