Differences Between a Baby, Newborn, Infant, & Toddler

difference between newborn, infant, and toddler

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The English language has several terms for children between the ages of birth and 4 years, including newborn, infant, baby, and toddler. These terms are often used interchangeably for various ages of young children and may mean different things to different people. Here's a look at each of these terms, what age range they apply to, and an overview of the growth and development you can expect during that time.

Babies, Newborns, and Infants

Though the terms "baby," "newborn," and "infant" are frequently used synonymously, the exact definition depends on the source you consult.


  • Newborn usually refers to a baby from birth to about 2 months of age.
  • Infants can be considered children anywhere from birth to 1 year old.
  • Baby can be used to refer to any child from birth to age 4 years old, thus encompassing newborns, infants, and toddlers.

The Merriam-Webster dictionary simply says a newborn is a child who is recently born and does not put an upper limit to the term. Merriam-Webster also defines an infant as a child in the first stage of life but doesn't give any age specifics and describes 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.

The Centers for Disease Control and Prevention (CDC) defines an infant as from birth to 1 year old. The CDC calls 1 to 3 year olds toddlers and kids 3 to 5 year old preschoolers.

Growth and Development

Between birth to 1 year of age, babies grow and develop at an astounding rate. They learn to smile, roll over, sit up, wave, clap, pick objects up, crawl, babble, and some may even start saying a few words.

They learn to bond with and trust their caregivers and they often understand more than they are able to communicate. Babies enjoy music, movement, and simple games like peek-a-boo.

By the end of this period, many babies are standing up and walking around holding onto furniture, if not walking completely independently. They've also typically tripled their birth weight and grown around 6 to 8 inches by the time they're a year old.

Areas of Concern

Babies develop at different rates, and it is normal for them to reach milestones at very 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 is a need for further evaluation. Take note if your baby seems to lag behind 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

When Is a Baby Considered a Toddler?

A baby is considered a toddler around 1 year (12 months) of age and is typically considered one until around 3-years-old. As the name implies, a toddler is classically defined by the Merriam-Webster dictionary as a child who is just learning to walk or one who toddles.

There's no official definition of the upper limit of toddlerhood; however, most people consider the end of the toddler age to be around the time a child is ready to transition into preschool, around 4-years-old.

The CDC considers children who are ages 3 to 5 years old to be preschoolers.

Growth and Development

As babies move into their second year of life, they become more mobile and more independent, exploring everything they can access. Nearly all children are walking by 18 months. They're also learning to talk, to identify and imitate the people around them, and to follow simple instructions.

As they get older, they learn to express more emotions, speak in phrases and sentences and can help get themselves dressed and ready for the day. They enjoy simple games, songs, and rhymes, and they can start learning their colors, shapes, and alphabet.

Like little sponges, toddlers soak up everything, so memorization comes fairly easily. They still need a lot of sleep and may take a nap or two during the day, as well as sleep 10 to 12 hours a night.

By 3 years old, the average toddler has usually reached between 53% and 57% of their adult height.

Areas of Concern

Again, it is completely normal for toddlers to develop at different rates. But do check with your pediatrician if your toddler isn't meeting developmental milestones, such as:

  • Walking
  • Holding lightweight objects
  • Chewing and swallowing food
  • Adding new words to their vocabulary regularly
  • Showing interest in you and other familiar people
  • Using two-word phrases (by age two)
9 Sources
Verywell Family 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.
  1. World Health Organization. Infant, Newborn.

  2. Centers of Disease Control and Prevention. Infants (0-1 year of age).

  3. Centers for Disease Control and Prevention. Toddlers (1-2 years of age).

  4. Centers for Disease Control and Prevention. Toddlers (2-3 years of age).

  5. Centers for Disease Control and Prevention. Preschoolers (3-5 of years).

  6. Centers for Disease Control and Prevention. Toddlers (2-3 years old).

  7. Centers for Disease Control and Prevention. Preschoolers (3-5 years of age).

  8. Centers for Disease Control and Prevention. Important Milestones: Your Child by Eighteen Months.

  9. Centers for Disease Control and Prevention. Important Milestones: Your Child by Three Years.

Additional Reading

By Heather Corley
Heather Wootton Corley is a mother, freelance writer and certified Child Passenger Safety Technician-Instructor.