At what age is a child expected to achieve 100% intelligibility in speech?

Achieving 100% intelligibility in speech typically occurs around the age of 4 years. At this age, children are expected to have developed clear articulation skills and an understanding of phonological patterns that allow them to be completely understood by unfamiliar listeners. Prior to this age, while many children can be understood in familiar contexts, they may still exhibit unclear speech sounds or use simpler structures that can make it difficult for a stranger to comprehend them fully.

By age 4, language skills have usually matured to a point where pronunciation is clearer, and the vocabulary and sentence structures are more complex, contributing to complete intelligibility. At ages 2 and 3, children may often be understood by parents or caregivers who are familiar with their speech, but they may not reach full clarity until they are closer to 4 years old. By age 5, children typically refine their language skills even further, but full intelligibility is mostly expected by 4 years.