At what age should children start to speak in full sentences?

Children typically begin to speak in full sentences around the age of 3 years old. At this stage of development, they have usually acquired a vocabulary of about 200 to 1,000 words and can combine words to form simple sentences. For instance, they might start using two- or three-word phrases to express their needs or thoughts, such as "want cookie" or "go outside."

By age 3, children also start to grasp the basic structure of sentences, including the subject-verb-object order. This is a critical period where the foundation for more complex language skills is built, as their language abilities continue to develop rapidly. As they approach 4 years old, children's sentences become longer and contain more complex grammatical structures, but the milestone of speaking in full sentences is generally recognized at around age 3.

Other options represent developmental milestones that are either earlier or later than the typical age for speaking in full sentences, which could lead to misunderstandings about language development timelines.