After several months of speech that is restricted to short utterances, children enter the "telegraphic stage" and begin to produce longer and more complex grammatical structures (O'Grady & Cho, 2011, p. 347). This stage is characterized by production of complex structures as children begin to form phrases consisting of a subject and a complement in addition to use of modifiers and composition of full sentences. Children use mostly content words and their sentences lack function words. For example, a child may say "fill cup water," instead of saying, "Fill my cup with water." Subsequently, language acquisition continues to develop rapidly and children begin to acquire complex grammar that shows understanding of intricate linguistic features, such as the ability to switch the position of words in sentences.