Understanding first words
Babies understand some words well before they say any. Many understand common words like "no" and their parents' names by about 6 to 8 months, and nearly all understand at least 10 words by their first birthday.
How sure are we?
Very sure. Studies in many countries agree, using both parents' reports and lab tests of where babies look, though parents' reports for young babies may be a little high. How we know this
What it’s a sign of
Your baby is linking the sounds of everyday words to the people and things they stand for, often before saying any words.
Researchers used to think babies started understanding words between about 9 and 15 months. Studies that watch where babies look when a word is said have found understanding from about 6 months. Parents' reports of what young babies understand can be surprisingly high, and researchers aren't sure how accurate they are. The CDC lists looking at a familiar object when you name it at 15 months, later than the ages above, because it uses the age by which about 3 in 4 children do it, rounded up to the next check-up.
Understanding is harder to measure than talking, because babies can't tell us what they understand. We don't know exactly how many words babies understand at the very start.
A main source for the ages
Similarities and differences in child development from birth to age 3 years by sex and across four countries: a cross-sectional, observational study
Ilgi Ozturk Ertem, Vibha Krishnamurthy, Mphelekedzeni C. Mulaudzi, Yanina Sguassero, Hakan Balta, Ozlem Gulumser · 2018 · Lancet Global Health
- Children
- About 4,900 healthy children
- Where
- Argentina, India, South Africa and Turkey
- Ages
- Birth to 3½ years
- How
- Trained staff asked parents open questions about what their child could do, at health clinics
- What it found
- Found the age by which half of children reached more than 100 milestones. Most came at similar ages in all four countries, and for boys and girls. For example, half of children waved bye-bye by about 11 months and said a first word by about 9 months.
- Limits
- Only four countries and no rural areas, children from city clinics, and only healthy children (about half of those who came were left out for health reasons). It gives the age for half of children, not the full spread.
A main source for the ages
Words children say and understand, by age, in many languages: our count from Wordbank v3.4
MyHappyBub (analysis of Wordbank open data) · 2026
- Children
- About 134,000 toddler word lists and 50,000 baby word lists, in more than 30 languages
- Where
- Families speaking more than 30 languages; the most from the United States
- Ages
- 8 to 36 months
- How
- Our own count from parents' word lists in the open Wordbank collection
- What it found
- In American English, half of children said at least 50 words by 18 months and nearly all (95 in 100) by 27. More than 9 in 10 parents said their 8-month-old understood at least one word, and nearly all babies understood at least 10 words by 12 months.
- Limits
- Parents tick words on a list, which probably misses some words. Each month is a different group of children. Parents' reports of what young babies understand can be surprisingly high.
A classic study on this
At 6–9 months, human infants know the meanings of many common nouns
Elika Bergelson, Daniel Swingley · 2012 · Proceedings of the National Academy of Sciences
- Children
- Babies aged 6 to 9 months (number not checked yet)
- Where
- Not checked yet (summary only)
- Ages
- 6 to 9 months
- How
- Researchers tracked where babies looked when a parent named one of several pictures
- What it found
- Babies from 6 months looked at the picture that was named, showing they already understood several common words learned at home.
- Limits
- A lab study. We read the summary, not yet the full paper.
A study that questioned earlier findings
Infants who are rarely spoken to nevertheless understand many words
Ruthe Foushee, Mahesh Srinivasan · 2024 · Proceedings of the National Academy of Sciences
- Children
- Babies in a Tseltal-speaking community (number not checked yet)
- Where
- A Tseltal-speaking community in southern Mexico
- Ages
- Not checked yet
- How
- Researchers tracked where babies looked when words were said
- What it found
- Babies who are rarely spoken to directly, but hear a lot of talk around them, still understood common words, as US babies do.
- Limits
- One community. We read the summary, not yet the full paper.
A main source for the ages
Variability and Consistency in Early Language Learning: The Wordbank Project
Michael C. Frank, Mika Braginsky, Daniel Yurovsky, Virginia A. Marchman · 2021 · MIT Press
- Children
- About 82,000 word lists filled in by parents
- Where
- 29 languages, mostly from Europe and the United States
- Ages
- 8 to 30 months
- How
- Researchers pooled parents' word lists from many studies (the Wordbank collection)
- What it found
- Gives "around one year" as a rule of thumb for first words, and shows that children of the same age vary a lot in how many words they say.
- Limits
- Parents can miss words or count babble as words. Most children were from Europe and the United States and learning one language.
A main source for the ages
Evidence-Informed Milestones for Developmental Surveillance Tools
Jennifer M. Zubler, Lisa D. Wiggins, Michelle M. Macias, Toni M. Whitaker, Judith S. Shaw, Jane K. Squires, Julie A. Pajek, Rebecca B. Wolf, Karnesha S. Slaughter, Amber S. Broughton, Krysta L. Gerndt, Bethany J. Mlodoch, Paul H. Lipkin · 2022 · Pediatrics
- Children
- A review of 34 studies and common checklists, not one group of children
- Where
- Studies from many countries (14 of the 24 with age data were from countries where English isn't the main language)
- Ages
- 2 months to 5 years
- How
- Experts reviewed studies and checklists, then placed each milestone at the check-up age by which about 3 in 4 children do it
- What it found
- Places calling a parent "mama" or "dada" at 12 months, and saying 1 or 2 other words at 15 months. These are ages by which about 3 in 4 children have started, rounded up to a check-up age.
- Limits
- Experts' judgement set the ages, and some milestones rest on opinion rather than measured ages. The lists haven't been tested to see whether they help.
If you’re worried about your child, talk to your child and family health nurse or GP.
Last checked 2 November 2026