The rate of children's speech and language development can vary, depending on the child. Some children will develop certain skills quicker than others, and some children will be slow to develop certain skills compared to their peers, even if there are no related problems. This information is just a general guideline, and many experts vary considerably on what they believe to be the normal stages of development.
You will see that many skills mentioned are repeated over several age groups as children are all different and some take longer to develop these abilities. So just use this information as a very general guideline rather than read too much into it. There also may be some difference between boys and girls and when they develop certain skills.
To try and make these milestone information sheets easier to read I have created a made-up child called Bill. Bill was lucky, he had a childhood free of any illness or accidents and he had proactive parents who played with him and gave him lots of quality 1:1 attention and play-time. Bill has normal hearing.
17-Oct-2015 3:24 PM (AEST)