Open nearly any parenting book, and you'll find a list of early childhood milestones which describe the average age at which kids accomplish things. Each child develops differently, though. If your child lags a little in an area such as intellectual development, keep an eye out. If the lag becomes significant, you should seek professional help.
0 to 1 Year
Your child will seem to leap from milestone to milestone during his first year. From birth to 4 weeks, he'll glance at your face. From 1 to 3 months, his attention span will increase, he'll coo, and he'll smile when he sees your face. Between 3 and 6 months, he'll vocalize some sounds, and he'll start saying "mama" or "dada" between 6 and 9 months. From 9 to 12 months, he'll understand basic commands and imitate sounds.
1 to 2 Years
During his second year, your child will begin sorting things by shape and color, according to the Centers for Disease Control and Prevention. She will be able to find objects even when they're hidden under something. She should use several words by 18 months and several phrases by 2 years. She'll also recognize the name for many people and objects.
2 to 3 Years
From 2 to 3 years, your child will be able to avoid some hazards to keep himself safe. He will be fascinated by learning and will often ask what things are. He'll start using sentences of up to four words, and his vocabulary will include about 1,000 words.
3 to 4 Years
Between 3 and 4 years old, your child should be able to understand what counting is and know some numbers. She can name at least a few colors and remember some parts of stories that are read to her. Her vocabulary will reach about 1,500 words.
4 to 5 Years
By the time he's 5, your child will speak about 2,000 words, and will use hundreds of words in sentences that become increasingly longer, according to the Raising Children's Network. He'll start developing a feeling for time, such as how long something takes. He'll have more questions than ever; enjoy rhymes and silly sounds; and may begin to argue with his parents when they tell him what to do.