You Will Need To Issue Gentle Reminders At First
At this stage, it will still take some time for your kid to remember to use proper words that fit the situation, whenever appropriate. Do not show your annoyance if they forget, just keep reminding them gently. Be sure to praise the child when they do incorporate these terms in their behavior. When your child is learning to speak, he will automatically pick up words that he hears from you or people around him.
However, for his tender age, it might be impossible to keep a track of all the words that he hears around him. The best way to tackle this situation is to pump out the words that he is omitting while speaking in a slow manner. Do not jump in to help in instantly all the time but while you do it, make sure that your child repeats the words after you. The habit will help him remember the words and the mistakes that he committed last time. Gently, try to remind him of the words that he is missing out on.