At what age is 90% of adult syntax acquired?

By the age of five, children typically demonstrate a high level of proficiency in adult syntax, with about 90% of the syntactic structures they will use as adults being acquired. This early age marks a critical point in language development, where children transition from basic sentence structures to more complex forms.

At this stage, children are not only expanding their vocabulary but also mastering the rules of grammar and sentence formation. By five years old, they can generally produce longer and more varied sentences, use conjunctions, and apply appropriate tense and plurality in their speech.

This proficiency sets the foundation for further language development, allowing for the effective communication of more sophisticated ideas and thoughts as children grow.