I just told someone on parenting that a baby becomes a toddler when it starts moving around. The question which came back was "what age does a toddler stop being a toddler?".

That got me searching, and I found at least one reference that said "Toddlers are babies from one year to four years of age".

I'd never consider a four-year-old as a baby. Is this just me, or a geographical difference?

  • 1
    To some degree, a toddler is a type of baby: specifically, a baby that has learned to walk. (Not just move around: a crawling baby is not yet a toddler.) There does come a point, though, when a child can be called a toddler, but not really a baby. I'm not sure when that point is - maybe when the toddler has learned to speak in a semi-understandable fashion?
    – Martha
    Commented Nov 28, 2011 at 15:03
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    @JeffAtwood: what gives? How was this question off-topic for EL&U? Commented Nov 28, 2011 at 19:21
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    @Martha: I'd put the cutoff for "baby" at toilet training. A toddler in diapers is still a baby. A toddler who yells for you to come wipe is no longer a baby.
    – JPmiaou
    Commented Nov 28, 2011 at 22:13
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    I'd just like to clarify something. @JeffAtwood seems to be taking the question from the first paragraph and believes that that is the question, whereas I'm reading that that as a starting point that led to the question "Can a toddler be simultaneously categorized as a baby?" (i.e. Jeff is reading this as when someone moves from C to D in this chart I just made whereas I'm reading it as whether B exists or not). Benjol, would you mind clarifying this?
    – waiwai933
    Commented Dec 3, 2011 at 7:20
  • 5
    I speak French and we don't have, to my knowledge, this distinction. There is actually no direct translation of that word to French. So that might indeed be a language-related question rather than a "parenting" one, me and my wife being parents but totally unable to have that debate you had @JeffAtwood
    – Laurent S.
    Commented Jul 15, 2015 at 20:23

9 Answers 9


I don't think there's a universal definition.

Going by the American Academy of Pediatrics:

  • Baby = 0 - 1 year (Sometimes called "Infant" in other sources)
  • Toddler = 1 - 3 years (Some still consider young toddlers to be 'babies')
  • Preschooler = 3 - 5 years
  • Gradeschooler = 5 - 12 years (Sometimes called 'school age' in other sources)

Clothing manufacturers, on the other hand, consider toddlers from 2 - 4, which is why you see 2T - 4T clothing sizes.

I would say the real test is based on developmental milestones rather than age. A child is a toddler once they begin walking/toddling around, and ceases to be a toddler when they have met a number of milestones such as communication, toilet training, and motor skills.

  • 2
    Good citation. Not sure why the other answers are being upvoted when they are little more than "here's what I think.." Commented Nov 28, 2011 at 18:49
  • As near as I can tell, the T in children's clothing sizes indicates diaper access. I'd expect crotch snaps on size 4T overalls, but not on size 4 overalls. Of course, like clothing sizes in general, it all depends highly on the manufacturer.
    – JPmiaou
    Commented Nov 28, 2011 at 22:10
  • @JPmiaou: Yeah, according to a clerk at Childrens' Place, the only difference between 4 and 4T was "there's extra room in the pants for the diaper". But I expect you're right that it depends on manufacturer.
    – Lynn
    Commented Nov 28, 2011 at 23:07
  • This is also essentially the definition we use on this site. See the tags page. Commented Nov 30, 2011 at 20:05
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    +1 for the link, and for "the real test is based on developmental milestones". The milestones are far more important than chronological age, considering how much variance there is in children meeting those milestones.
    – user420
    Commented Nov 30, 2011 at 20:10
  • Infant: 0 - 1
  • Toddler: 1 - 3
  • Pre-Schooler: > 3

While it can vary to some extent based on a child's development; the above is fairly common across the US.

Baby on the other hand is an umbrella term and has no distinct cut off point.


Neither toddler nor baby are defined strictly according to age. I would take them to be mutually exclusive, using the definition that a baby is a very young child who has not learnt to walk while a toddler is a young child who has just learnt to walk.

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    I would make this distinction between infant and toddler, not between baby and toddler. In my lexicon, an 18-month-old is still definitely a baby, while also definitely being a toddler.
    – Martha
    Commented Nov 28, 2011 at 17:02
  • @martha OK cool.
    – Jasper Loy
    Commented Nov 28, 2011 at 17:30
  • @Martha, this may be a UK/US difference - in the UK the first two years of school are "infants" (or were back in my day, which is admittedly an increasingly long time ago...)
    – Benjol
    Commented Nov 28, 2011 at 20:57

To me, the word "toddler" emphasizes a characteristic gait or style of movement, toddling. Toddlers are mobile, but their movement is a little awkward and inefficient. Adults don't trust toddlers to have an accurate sense of their own physical limits, and so toddlers require fairly close supervision to keep them from hurting themselves.

I think a child ceases to be a toddler when their motor skills develop and they move more like adults, and when they understand their bodies well enough to need less vigilance for physical safety.

Related to this I think is a change in developmental focus: a large part of a toddler's learning is around movement and motor skills. A pre-schooler has reached a level of dexterity where movement is no longer a primary developmental focus.

This transition from toddler to pre-schooler is gradual, of course; there's no hard cutoff. I agree with the other answers that this transition often happens in the 2-3 year range.

Disclaimer: I don't have a background in child development; my answer is based on my own experience.


The term Toddler is pretty definitive and self defining. "Baby" is much more ambiguous, and can be applied over a range of ages, so yes, they certainly can overlap. I don't consider a four year old a baby either, but I know an almost two who is very much a toddler (busily running everywhere) but who is typically referred to as baby.

  • A toddler is...one who toddles.
    – Wildcard
    Commented Jul 14, 2017 at 4:25

According to developmental studies (and don't ask me why age 5 is an overlap, I am not the one who created these):

  • Newborn 0-3 months
  • Infant 4-12 months
  • Toddler 13 months to 35 months
  • Preschooler 3-5 yrs
  • Kindergartener 5-6 yrs (I included this because it is good to know.)

I kind of agree with last two I guess 5 can fit in both slots. But yeah they kind of got cruddy names for developmental stages but what ya gonna do about it. I have mass pet peeve with clothing manufacturers and the T but I do understand maybe not wanting to put letter p on clothing. Newborn is also fine. However I find infant and toddler very broad age group, is your 4 month old same as your 9 month old, probably not.

For me I have added couple things to infant and toddler area because I see the difference that science hasn't quite caught up to.

  • Infant 4-6 or 7 months obviously every child is different
  • Pre toddler 7 or 8 months-12 months
  • Young toddler 13months- 23 months
  • Older toddler 24 months to 35 months.

The rest is reasonable as is.

The term baby can be numerous things depending on circumstances.

I don't know why but it bugs me when a parent calls their 3, 4, or 5 yr old a toddler when they really aren't. If you want more general way to refer to children: baby 12 months and under, toddler 1-2. Little child/kid 3-6 yrs, big child/kid 7-9 yrs, tween/preteen 10-12. Though don't be surprised if 3-6 says I am big — they want to be bigger then they are.


They are definitely not mutually exclusive in at least one instance: when referring to "the baby" (of the family), you are referring to the youngest child, regardless of age. In that sense, "the baby" might be a toddler or even a child or teenager.

  • Very good point. A lot of times the "cutoff point" for no longer being called a baby is when they get a younger sibling, or maybe cousin. Commented Nov 29, 2011 at 4:19
  • I think that in this context, baby is more metaphoric. Like saying "don't treat me like a baby", "stop being a baby"
    – learner101
    Commented Apr 27, 2017 at 12:46

I think in common usage, a toddler can be baby that can walk or a young child. A baby becomes a toddler when they can walk, but you can still call them a baby until they are maybe two years old. You can call them a toddler until they turn 4.


The terms 'baby' and 'toddler' would not be used of a child simultaneously but because of their vagueness might overlap if applied logically. Some sources give definitions by age that do not overlap, but that is an artificial division.

  • a baby (or synonymously an infant) is a child that has just been born and cannot yet talk (incidentally to around 1 year old when they start to talk)
  • a toddler is a child that has just learned to walk (and this incidentally occurs around 1 year of age)

The upper limit between a toddler and just a very young child is much vaguer, I think of it as literally when the child is well-balanced (that is not 'toddling' any more). A four year old doesn't seem to be a toddler any more but a three year old might be. Even a two year could get away with not being a toddler and instead just a very young child.

But despite the logical fact that one might be able to talk but not yet able to walk or walk and not talk (in the varying ways that abilities develop in a child), one would be hard pressed to label a child both a baby and a toddler. If you can walk, you're not a baby any more, you're a toddler. If you can speak but can't yet walk, you'd probably still be labeled a baby (though maybe not an infant).

  • I disagree that "baby" is synonymous with "infant". Our 1 year old toddler is still a baby, but definitely not an infant. "Infant" is a subset of "baby".
    – user420
    Commented Nov 30, 2011 at 20:07
  • I disagree about "infant = baby" too. On this site, our definition of "infant" is roughly the period of 3-12 months of age. Commented Feb 28, 2013 at 6:38

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