Your child has now entered his schooling phase and is open to interacting with children of his age. You as a mother need to train him so that he can perfect his speech in order to express exact feelings and thoughts. He's now ready to learn more about size concepts, color concepts, etc.
What you need to know
Once the child has learnt to converse in a decent manner then you must help him understand about various concepts. These concepts include the learning of comparative and superlative adjectives. You can practice this by making the little one learn about things which are big, bigger and biggest. Take three balls of different sizes and teach the child to use the exact adjectives to describe their size.
The next phase can be to make him understand time concepts, for example- today, tomorrow, yesterday, next, last week, days of the week etc. Make sure you are patient with the child while you impart this knowledge. Never force the kid to learn as it might make the child grow stubborn. Enhance the level of conversation and include these concepts so that the kid can develop a good understanding.