Hello!

It will not be a discovery that is terribly pleasant when the child uses polite words in everyday communication. However, the two-year kid still does not quite understand the nuances of the use of these words. It turns out that talking "good night" needs not only mom and dad, but also grandmother too.
Our books are built on repetitions. In the same situation, the characters change with whom the protagonist communicates, and in each this case the same "magical word" sounds so that the baby remembers him.
The memorization passes easier if the verbal shape is supported by a non-verbal gesture. If he, of course, is available. For example, Masha when goodbye or press the hand, welcoming.
Remember that the best learning is a personal example! Do not forget and never tell your baby "Hello" and "Goodbye"!