It is important to remember that developmental charts are only a guide to the ages and stages of development. They are not perfect for every child. All children are individual and unique; they will progress roughly in the same order but not necessarily all at the same speed as their peers.

Observe three children of the same age and make a note of their conversational style.
What words do they use?
Do they use sentences?
Is the range of vocabulary equal or does it vary according to gender, topic, or time of day?