At the end of their second year, toddlers begin communicating in two- to four-word sentences. This process begins when children start combining single words with a gesture or grunt, or when they shape a question by raising their arms, saying, "Up?" and raising their voices.  Next, children combine verbs or prepositions with nouns to make statements. Although the process is highly individualized, most toddlers have mastered more than 50 spoken words and can talk in short sentences by the end of their second year.