This lecture discusses phonological development in children from ages 1 to 7. It outlines the stages of crying, cooing, and babbling in the first year. By age 2 1/2, children have mastered most vowels and 2/3 of consonants, with difficulty remaining for a few consonants by age 4. Sounds are used correctly first at beginnings of words. To make words easier, children may delete or substitute sounds. While speech may lag comprehension, studies show children can understand sounds they cannot pronounce. Intonation understanding continues developing into the teenage years.