What developmental milestone occurs around the age of nine months in relation to verbal expression?

At around nine months of age, a key developmental milestone in verbal expression is that infants start babbling. Babbling typically consists of repeated consonant-vowel combinations, such as "ba-ba" or "da-da." This stage of vocal development is crucial as it represents the early foundations of speech, allowing infants to practice the sounds and rhythms of language. Babbling also serves as a form of communication, helping infants engage with caregivers and express their needs and emotions.

In contrast, speaking in one-word utterances typically occurs later in development, around the age of 12 months or so, when infants can begin to use single words meaningfully. Understanding language is a gradual process that develops simultaneously with verbal skills and generally progresses with increased exposure to spoken language well beyond the nine-month mark. Copying sounds may occur around this age, but it often becomes more pronounced as the child approaches their first birthday, as they start to mimic the sounds they frequently hear in their environment.