Final answer:
A baby's vocabulary and ability to string words together increase as they grow older, with toddlers typically being able to use between 50 and 200 words by the age of 2 and up to 1,000 words by the age of 3.
Step-by-step explanation:
The number of words a baby can string together per year of life varies based on their age. By 2 years old, a toddler can use between 50 and 200 words. By 3 years old, their vocabulary can reach up to 1,000 words and they can speak in sentences. However, it is important to note that the rate of vocabulary growth can differ among children.