What is the term used to describe infants?

The term used to describe infants is typically defined as those who are until 1 month old. In pediatric care, the neonatal period refers specifically to the first 28 days of life, and the term "infant" is often used interchangeably during the subsequent months but generally includes anyone from birth to 1 year old. However, it is most commonly recognized that the earliest stage, the first month of life, is crucial because it encompasses vital developments that occur immediately after birth.

Therefore, defining infants as "until 1 month old" captures that early, critical phase of development. While the other choices encompass broader age ranges, they extend beyond the more specific definition of infancy, thereby making them less precise for this nomenclature.