Research consistently shows that multilingual children reach language milestones on a similar timeline as monolingual children. But their journey may look a little different.

If you are raising a multilingual child, you may notice that their words come from different languages, that they mix languages within the same sentence, or that one language seems stronger than another.

All of these are completely normal. They are not signs of confusion, on the contrary, they are expected stages of multilingual development.

Understanding how multilingual development works can help you see your child’s progress more clearly and support it with confidence.

Same milestones across more than one language

Multilingual children follow the same general developmental stages as all children but their skills are distributed across the languages they hear and use.

Here’s what this often looks like:

6–12 months

Babies babble using sounds from all the languages they are exposed to (e.g. “ba-ba”, “da-da”, “ma-ma”, or early approximations like “baba” for banana).

This is an important early sign of language development even when different sound systems are present.

Read more on first multilingual non-verbal communication milestones here.

12–18 months

First words begin to appear sometimes in one language, sometimes across multiple languages (e.g. “milk” in English, “leche” in Spanish).

At this stage, what matters is meaningful word use, not which language the word comes from.

18–24 months

Vocabulary grows rapidly across languages.

A child may seem to know fewer words in each individual language, but their total vocabulary (across languages) is often comparable to monolingual children.

2–3 years

Children begin combining words into short sentences and expressing more complex ideas.

Mixing languages within the same sentence (code-mixing) is very common at this stage and is a normal part of multilingual development, not a sign of confusion.

What happens next? (3+ years)

As children grow, their language development becomes more complex across all their languages.

Around 3 years

Children begin mastering basic grammatical patterns, such as verb forms and plurals.

It is very common to hear “mistakes” that actually reflect rule-learning (e.g. ‘runned’ instead of ‘ran’, ‘eated’ for ‘ate’)

These are called overgeneralizations: children are applying rules correctly, just too broadly.

4–4.5 years

Children expand their vocabulary and start using words more flexibly, though meanings are not always fully refined.

They may overextend or slightly misapply words as they build understanding.

Example: Using cup for any drinking container (glass, mug, bottle)

This shows that children are actively organizing meaning, not that they are confused.

Around 6 years

Children start using more complex and abstract language, with structures that resemble adult speech.

In multilingual children, this development may appear uneven across languages depending on exposure and that is completely normal.

Key takeaways

Not all children develop language at the same pace. Some progress faster, others more gradually, and some may show temporary delays in early language development.

Importantly, many children who start speaking later go on to develop typical language skills over time.

Language development is shaped by a dynamic interaction between biological maturation and learning through experience.

As Lev Vygotsky emphasized, language develops through social interaction and especially through everyday communication with caregivers.

Multilingual development may look different, but it follows the same underlying path as monolingual development.

What matters most is overall communication, understanding, and interaction, not perfectly separated languages.

Is mixing languages a problem?

Many parents worry when children mix languages in the same sentence:

“I want more leche”

This is called code-mixing. And it is completely normal! Read more about code mixing and code switching here. 

Research shows that:

• It is not a sign of confusion
• It is a natural communication strategy
• It reflects linguistic flexibility and competence

Multilingual children use all their linguistic resources to express themselves, exactly as they should.

What research tells us

Decades of research in Bilingualism show that:

• Multilingual children are not delayed overall in language development
• Their vocabulary is distributed across languages, not duplicated 
• Their brains develop flexibility in language use and processing

As François Grosjean explains, bilinguals are not “two monolinguals in one,” but individuals with a unique and integrated linguistic system.

Similarly, Ellen Bialystok highlights the broader cognitive benefits associated with multilingualism, including attention control and flexibility.

Annick De Houwer has shown that bilingual children are not inherently at risk for language delay simply because they are exposed to more than one language. Instead, their development depends largely on the quantity and quality of input they receive.

When should you seek support?

While multilingual development is natural, it is important to look at overall communication, not just one language.

You may want to seek professional advice if:

• Your child uses no words by around 18 months (in any language)
• Your child does not begin combining words by 2.5–3 years
• There are concerns about understanding language

These indicators apply to all children, regardless of how many languages they are exposed to.

What about language mixing?

While mixing languages is a normal part of multilingual development, there are a few situations where it is worth observing more closely.

You may want to look more carefully if:

• Your child consistently mixes grammatical structures from one language into another in a way that sounds “off” and cannot be explained by either language
• Your child uses the sentence structure of one language while speaking another over a longer period of time, even when not tired or under pressure
• Communication becomes frequently unclear or difficult to understand, even for familiar listeners

As Ute Limacher-Riebold highlights, factors such as fatigue, transitions between languages, or complex situations can temporarily increase mixing and this is often normal.

Before worrying

Before seeking support, it can help to:

• Slow down the pace of interaction
• Give your child time to respond
• Ask open questions to clarify meaning
• Support communication without pressure

If concerns persist, consulting a professional familiar with multilingual development is recommended. You can read more about code-switching and what to do when you are worried here. 

What really supports multilingual development

You don’t need perfection, you need consistency and meaningful interaction.

What helps most:

• Regular exposure to each language
• Real communication (not just passive listening)
• Emotional connection with the language
• A supportive, pressure-free environment

A different kind of growth

Multilingual development is not slower. It is broader.

Children are not just learning words, they are learning how to move between languages, cultures, and contexts. And that is a powerful skill for life.

References & further reading

Grosjean, F. (1989). Neurolinguists, beware! The bilingual is not two monolinguals in one person. Brain and Language, 36(1), 3–15.
https://www.francoisgrosjean.ch/bilin_bicult/3%20Grosjean.pdf

Bialystok, E. (2009). Bilingualism: The good, the bad, and the indifferent. Bilingualism: Language and Cognition.
https://doi.org/10.1017/S1366728908003477

De Houwer, A. (2009). Bilingual First Language Acquisition. Multilingual Matters.

⇒ You can also explore the 10 stages of bilingual language development here.