Final answer:
Federal regulations define "children" in different age groups based on age brackets provided by the U.S. Census Bureau.
Step-by-step explanation:
The federal regulations define "children" in different age groups. According to the U.S. Census Bureau, children are categorized into several age brackets: 0 to 2.5 years, 2.5 to 6 years, 6 to 13 years, and 13 to 20 years. These age ranges help provide a clearer understanding of child demographics and help shape policies and programs related to child welfare and well-being.