Final answer:
The 18-month-old child's statement 'want puppy' when pointing to a picture of a dog is an example of telegraphic speech, a stage where children use simple sentences with only essential words.
Step-by-step explanation:
When the nurse practitioner observes an 18-month-old child point to a picture of a dog and say "want puppy," this behavior is an example of telegraphic speech. Telegraphic speech occurs when children begin to combine words to form simple sentences that contain only essential words. This developmental stage often omits small, less meaningful words, such as "is," "and," or "the." At 18 months, children are beginning to combine words to communicate more complex ideas, though their sentences are still quite rudimentary and functional.