Unfortunately, somewhere along the way your toddler learned the meaning of another word. Too bad children are not always perfect so we don't have to teach them this word. There are ways to deal with toddlers who talk back to their parents. First of all you must make your toddler understand that mom and dad are in charge. When your child talks back to you tell him firmly but gently that he cannot talk to you in that way.
Many children talk back to their parents for attention.
If you know this is your toddler's motive try ignoring him. Doing this will teach him that bad behavior will not get him any extra attention. These ideas take time to become successful but stick with them.