Final answer:
Babies usually start learning language between 9 months and 3 years old. They go through stages of cooing, babbling, and eventually saying their first words.
Step-by-step explanation:
Most babies undergo a rapid process of language learning between the ages of nine months and three years. Babies proceed through a set of stages that allow them to learn language just by being exposed to surrounding talk. Babies start cooing almost immediately, followed by babbling. At around 12 months old, babies say their first word and begin combining words for meaning at about 18 months.