Babies Differences Between a Baby, Newborn, Infant, and Toddler Ever wondered what age is considered a baby? How about a newborn, infant, or toddler? Here, we break down the differences. By Heather Corley Updated on February 14, 2024 Medically reviewed by Rachel Gurevich, RN Trending Videos Close this video player The English language has several terms for children between the ages of birth and 4 years, including newborn, infant, baby, and toddler. These words are often used interchangeably, and they may mean different things to different people. But what age is really considered a newborn? How about a baby, infant, or toddler? Here, we explore each of these terms and their age ranges. We also give an overview of the growth and development you can expect during each timeframe. What Age Is an Infant, Baby, and Newborn? Though the terms "newborn," "baby," and "infant" are frequently used synonymously, the exact definition depends on the source you consult. The Merriam-Webster dictionary simply says a newborn is an individual who was recently born and doesn't put an upper limit on the term. Merriam-Webster also defines an infant as "a child in the first period of life," but doesn't give any age specifics. They describe a baby as "an extremely young child." The World Health Organization (WHO) defines a newborn infant, or neonate, as a child that's under 28 days old. On the other hand, the Centers for Disease Control and Prevention (CDC) says the infant stages stretches from birth to 1 year old. Definitions Newborn usually refers to a baby from birth to about 2 months of age.Children can be considered an infant anywhere from birth to 1 year old.Baby can refer to any child from birth to age 4 years old, thus encompassing newborns, infants, and toddlers. Growth and Development Between birth to 1 year of age, kids develop at an astounding rate. They'll hit many milestones, which might include the following: Rolling over Smiling Sitting up Waving Clapping Picking up objects Crawling Babbling Possibly saying a few words Babies generally triple their birth weight and grow around 10 inches during their first year. During this time, they'll also learn to bond with their caregivers, and they understand more than they're able to communicate. Babies enjoy music, movement, and simple games like peek-a-boo. Areas of Concern Babies develop at different rates, and it's normal for them to reach milestones at different ages. However, if you are worried about your baby's development, check with your pediatrician. Your baby's doctor can reassure you or refer you to a specialist if there's a need for further evaluation. Take note if your baby seems to lag in these areas: Smiling Waving, pointing, reaching, and making other gestures with their hands Rolling over, crawling, or sitting up unassisted Babbling or otherwise attempting to communicate vocally Knowing and responding to their name What Age Is a Toddler? A baby is generally considered a toddler beginning around 1 year (12 months) of age. There's no official "upper limit" of toddlerhood, but most people consider the end of the toddler age to be around the time a child transitions into preschool. Indeed, the CDC says that kids ages 1 to 3 are considered toddlers, while 3- to 5-year-olds are preschoolers. The American Academy of Pediatrics (AAP) follows the same definitions. Toddler Growth and Development As kids move into their second year of life, they become more mobile and independent, exploring everything they can access. Here are some milestones you'll notice during the toddler years: Walking (usually by 18 months) Learning to talk (and eventually speaking in phrases and sentences) Identifying and imitating the people around them Following simple instructions Feeding themselves Engaging in play Expressing more emotions and awareness Imitating the behavior of others Running, kicking, and climbing as they near preschool age Like little sponges, toddlers soak up everything, so memorization comes fairly easily. They still need lots of sleep and may take a nap or two during the day, contributing to a total of 11 to 14 hours of sleep daily. Toddlers enjoy simple games, songs, and rhymes, and they can start learning their colors, shapes, and alphabet. Areas of Concern Again, it's completely normal for toddlers to develop at different rates. But check with your pediatrician if your toddler isn't meeting developmental milestones, such as: WalkingHolding lightweight objectsChewing and swallowing foodAdding new words to their vocabulary regularlyShowing interest in you and other familiar peopleUsing two-word phrases (by age two) Was this page helpful? Thanks for your feedback! Tell us why! Other Submit Sources Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Newborn health. World Health Organization. Infants (0-1 year of age). Centers for Disease Control and Prevention. Reviewed 2021. The Growing Child: 10 to 12 Months. Nationwide Children’s Hospital. Reviewed 2023. Toddlers (1-2 years of age). Centers for Disease Control and Prevention. Reviewed 2021. Preschoolers (3-5 of years). Centers for Disease Control and Prevention. Reviewed 2021. Ages & Stages. American Academy of Pediatrics. Important Milestones: Your Child by Eighteen Months. Centers for Disease Control and Prevention. Reviewed 2023. Important Milestones: Your Child by Three Years. Centers for Disease Control and Prevention. Reviewed 2023. A Consensus Statement of the American Academy of Sleep Medicine. Journal of Clinical Sleep Medicine. 2016. Additional Reading Centers for Disease Control and Prevention (CDC). Child Development: Positive Parenting Tips: Infants (0-1 Year of Age). U.S. Department of Health and Human Services. Updated May 23, 2018. https://www.cdc.gov/ncbddd/childdevelopment/positiveparenting/infants.html Centers for Disease Control and Prevention (CDC). Child Development: Positive Parenting Tips: Toddlers (1-2 Years of Age). U.S. Department of Health and Human Services. Updated January 3, 2017. https://www.cdc.gov/ncbddd/childdevelopment/positiveparenting/toddlers.html Hoecker JL. Infant and Toddler Health: How Much Should I Expect My Baby to Grow in the First Year? Mayo Clinic. Updated August 16, 2017. https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/expert-answers/infant-growth/faq-20058037 Purdy ER. Infant and Toddler Development. Encyclopedia Brittanica. Updated November 17, 2017. https://www.britannica.com/science/infant-and-toddler-development World Health Organization (WHO). Infant, Newborn. http://www.who.int/topics/infant_newborn/en/