At two years old, your child should be able to use around 50 words, and be able to name most objects that he or she sees or uses in every day life. Your child should also be able to follow two part instructions, make two-word sentences, and make him or herself understood to yourself and other caregivers. Some children at this age can point out body parts when they are named, and some may even be using pronouns like I, me or you, but these are usually not used correctly all the time.
At three years old, your child’s vocabulary should have expanded to three hundred words or more, he or she should be able to point out body parts when they are named, and will probably be able to provide his or her name and age when asked by someone. Your child may also be able to use plurals sometimes, make three word sentences, refer to some things in the past tense, and respond to questions. At this age, it’s likely that your child can be understood even by people who do not know him or her, and will often narrate his or her own play while it is happening. It’s not unusual for children this age to still have problems with pronunciation, but your child may also have mastered the use of pronouns by now.
At four years old, your child’s vocabulary will have leapt to one thousand words, and he or she can probably make sentences that comprise up to eight words. Naming objects in books should not be a problem for your four year old, and your child can probably also name at least three colors, and remember sequences of four digits, if you say them slowly and repetitively. Your four year old may also follow complex requests, although many children are only ready to follow three part commands. It’s likely that your child will still mispronounce words, however, he or she will be mastering adjectives and adverbs, and can probably also recognise common words like and, the, or a.