Start here
Many bilingual families are told to choose one language, often just when they are beginning to worry about their child’s development.
The short answer is no. Growing up with two languages does not cause a language delay or a language disorder. What it can change is how a child’s vocabulary looks when each language is counted separately. That distinction is where most of the confusion begins.
Our own children are growing up with Hebrew and Spanish. As a clinician, I know what the research says. As a mother, I also know that building two languages into an ordinary family life is rarely as tidy as the advice makes it sound.
Two languages do not cause a language disorder
Growing up with more than one language does not cause a language disorder, it does not confuse a child, and it is not a reason to drop a language.
The early milestones look much the same. Smiling, babbling, the first word, the first two-word combination: bilingual children reach these on a broadly similar timetable to monolingual children, and the two words in that first combination are allowed to come from two different languages.
The American Academy of Pediatrics puts it plainly to parents: using your own language will not confuse your child, hold them back at school, or stop them learning the majority language.
Why vocabulary may look different in each language
A bilingual child’s exposure is distributed across their languages. Because of that, their vocabulary may be smaller in each language when the languages are counted separately, especially in the language they hear and use less.
This is not the same as a language delay. The pattern depends on the amount and the quality of exposure, on who speaks each language, on where the child uses it, and on how much they need it in order to communicate.
A checklist designed for monolingual children may therefore make a typically developing bilingual child appear behind, if only one language is counted. When vocabulary is counted across all of a child’s languages, the overall picture is often comparable to that of monolingual peers.
How to count your child’s words
Count across all of your child’s languages, not one at a time.
Twenty-five words in Hebrew and twenty-five words in Spanish are 50 word forms across the two languages, not 25.
There are two ways to count, and they answer different questions. If your child says both “dog” and “perro,” those are two learned word forms that refer to one concept. Total vocabulary counts both words. Conceptual vocabulary counts the shared meaning once. Clinicians use whichever measure fits the question they are asking, and neither one is the “real” number.
For a practical list before an appointment: write down every meaningful word in every language, and note which language each one belongs to. That is one of the most useful things you can bring, and it lets the clinician decide which kind of comparison is appropriate. Parents are often surprised by their child’s total.
Mixing two languages in one sentence
A child who says “I want more mayim” is not confused, and they have not failed to separate their languages.
Adult bilinguals often mix languages too, especially with people who share the same languages. Mixing is systematic and sensitive to context: it may reflect who the child is speaking to, the topic, or simply which word is most available in that moment. It is not evidence that the languages have blurred together.
Even young bilingual children can become sensitive to which languages different people understand. Mixing may continue normally at any age, and it does not mean the languages are confused.
If it feels useful, you can naturally model the word in the other language, without asking your child to repeat it and without treating the mixed phrase as an error.
What actually makes the difference
There is no single perfect system. What matters most is how much meaningful exposure your child receives in each language, and how much of it involves them.
Meaningful exposure in each language
The amount of meaningful exposure a child receives in a language is consistently associated with their vocabulary and proficiency in that language. It is the least surprising finding in the field and the most useful one.
Exposure is not only a count of hours. Familiar speakers, conversational turns, the child’s need to use the language, and the richness of the interaction all matter.
Live, responsive interaction
Babies learn language most effectively through live, responsive interaction. Passive television or background audio in a language should not be counted as equivalent to time spent talking with a person who speaks it.
Older toddlers may learn some words or concepts from high-quality media, particularly when an adult watches and talks with them about it. A cartoon still cannot carry a home language on its own. Video calls are a different matter, because the person on the other end responds to your child in real time. There is more on this in screens and language before age two.
One-parent-one-language is not required
Many families feel they are doing bilingualism wrong because they do not hold to strict separation. In a questionnaire study of 1,899 families with children aged 6 to 10, the one-parent-one-language approach turned out to be neither necessary nor sufficient for children to actively use both languages. Home patterns in which the minority language was used more widely, where both parents used it and at most one parent used the majority language, had a high chance of the child actively using the minority language.
Which means: the family’s language pattern is associated with which languages a child actively uses. Strict separation is simply one strategy among several, and what you are really protecting is regular, meaningful exposure to the less-supported language and real chances to use it.
When it isn’t the bilingualism
Bilingualism is a convenient explanation, and it gets used to explain away things it did not cause. Some children are bilingual and also have a language disorder, in the same way that some children are bilingual and also need glasses. The second thing is not caused by the first.
The distinction clinicians work with: a language disorder generally shows up in all of a child’s languages, though it may not look identical in each. A weakness limited mainly to the less-exposed language is more consistent with a difference in exposure than with a disorder, and it still needs to be read in the context of your child’s full language history and skills.
Ask for an evaluation if:
- Your child seems behind in both languages, including the one they hear most.
- They have lost words or other skills they previously used, in any language. Contact their doctor promptly rather than waiting to see what happens.
- You have any concern about their hearing.
- They are not meeting the broader communication milestones, such as gestures, sharing attention, or understanding simple instructions.
- You remain concerned, even if your child’s pattern does not fit neatly into this list.
A standardized test given in only one language is not enough to judge a bilingual child’s overall language development. An evaluation should take account of every language your child uses, the amount and the context of exposure in each, what you report as a parent, and, where possible, language samples or assessment with a trained interpreter.
Questions parents ask me
Should we drop one language until they catch up?
Increasing exposure to one language may strengthen your child’s proficiency in that language. Dropping another language does not treat an underlying language-learning difficulty.
It also has costs. It can mean a parent ends up using a language in which they feel less fluent, less spontaneous, or less emotionally connected, which may reduce the rich, responsive interaction that language grows from. It can also cut a child off from relatives, from family relationships, and from an important part of their cultural connection.
My child understands both but only speaks one. Is that a problem?
It is a common pattern, especially when one language dominates outside the home, and it usually reflects where a child gets to use each language and where they need it. It is worth protecting the quieter language by giving it real, live use, and on its own it is not a sign of a disorder.
We started late with the second language. Is it too late?
No. Children add languages at many ages, and what it takes is frequent exposure and regular chances to use the language. Earlier exposure can make some aspects of language learning easier, and there is no single age at which the door closes.
Will my child fall behind in the majority language?
Regular exposure at daycare or school usually supports growth in the majority language. Keeping up the home language does not prevent that development, and strong skills in a family language can support communication, relationships, and later learning.
In many families the language at greater risk of being lost is the home or heritage one, because it gets less support outside the family.
Will a cartoon in the other language help?
Babies learn language best through responsive interaction with people, so a cartoon cannot replace a person speaking the language. Older toddlers may pick up some words from high-quality content, especially when an adult watches and talks with them, and it still cannot carry a home language on its own. A video call with a relative who speaks it is different, because they can respond to your child in real time.
The full guide
This page answers one question. From Babbling Baby to Talking Toddler is the whole picture in order, and it includes a chapter for homes with more than one language. It is written for general parent education, and it does not replace an individual evaluation.
About the guideMore on early language
- My toddler isn’t talking yet, what late talking means, and when to ask for an evaluation.
- Screens before two, why live interaction is not interchangeable with a recording.
- All the language tips.
About the author and sources
I am Michal Reshef, a speech-language pathologist licensed in Israel. I have worked with young children and their families since 2010, and I am a mother of three. I write about early language development for parents, and I am the author of the picture book Moving Soon and the parents’ guide From Babbling Baby to Talking Toddler. I am not licensed in the United States.
- American Academy of Pediatrics, Young Children Learning Multiple Languages: Parent FAQs, for the milestones, the combined vocabulary count, and the advice not to drop a family language.
- American Speech-Language-Hearing Association, Multilingual Service Delivery, for what an evaluation of a multilingual child should include, and why a standardized test in one language is not enough.
- De Houwer (2007), “Parental language input patterns and children’s bilingual use,” Applied Psycholinguistics 28(3), the questionnaire study of 1,899 families with children aged 6 to 10 which found one-parent-one-language to be neither necessary nor sufficient.
- Byers-Heinlein, Gonzalez-Barrero, Schott & Killam (2024), “Sometimes larger, sometimes smaller: measuring vocabulary in monolingual and bilingual infants and toddlers,” First Language, on why monolingual and bilingual vocabulary comparisons depend on how they are measured.
- American Academy of Pediatrics, Screen Time for Infants, for why live, responsive interaction is not interchangeable with passive viewing, and how a video call differs.
- American Speech-Language-Hearing Association, Communication Milestones.
Written and reviewed for clinical accuracy by Michal Reshef, a speech-language pathologist licensed in Israel. Last updated: September 2026.