By Jane Sonnenschein · April 18, 2026

A few days ago, I was talking with my husband about an essay I had just written. That essay explored a question: why do so many bǎomā¹ eventually come to believe that a person can have only one mother tongue?

The more I thought about it, I told him, the more I felt that the issue might not simply be that many parents believe, in principle, that there can be only one mother tongue. During childhood, many children genuinely have the opportunity to develop two native-language systems.

Both languages may already have begun to sprout and take root. Each may even have started forming its own pathways of expression. Yet as the child grows older, if one language becomes overwhelmingly dominant—used more frequently and present in school, friendships, the wider society and almost every corner of everyday life—the other language can gradually stop developing and may eventually be replaced, little by little.

It does not disappear all at once. It is more like a living plant that stops growing because another plant has taken most of the light, water and space. It no longer grows taller or spreads its roots. Eventually, it begins to wither.

I shared this thought with my husband simply because I wanted to discuss it with him. To my surprise, he agreed almost immediately.

“You are right to think of it that way,” he said.

Then he began telling me about his own experience and that of one of his friends. It was through this example that I suddenly understood something: when people later feel that they “really have only one mother tongue,” it may not be because the other language never truly existed. It may simply be because, in the years that followed, it was not allowed to remain alive.

My husband has a friend whose childhood background was very similar to his own. Both were born in the United States and moved to Germany when they were still young. Both lived near an American military base and attended German schools.

Yet their linguistic paths eventually became completely different.

Although my husband went to school in Germany, German children were not the only people around him. He also played with American children from the military base, and his circle of friends included both Germans and Americans. English was never interrupted in his life.

It was not something he had merely “learned as a child.” It remained a language that he continued to use, a language that continued to take part in his everyday life.

His friend’s experience was different. Over time, that friend began spending almost all his time with German children, and his social world became increasingly German-speaking. Although English had once been one of his languages, it gradually receded because he no longer used it regularly.

By adulthood, his English had deteriorated so severely that he could barely speak it.

At that point, I asked my husband the question I had really wanted to understand all along: if someone has already acquired two languages very well during childhood, at what age—and at what level—do those languages become truly secure?

Is there a point beyond which they will no longer deteriorate easily, even if they are rarely used later in life?

I had always assumed that there must be some kind of safety line. Perhaps by the time someone reaches their twenties, their linguistic systems have matured. Their vocabulary, intuition, cultural understanding and ways of expressing themselves have all developed. Would the languages not then remain securely within them?

A mother tongue, in particular, has always seemed to me to be more than simply something one can speak. It is connected to a person’s childhood experiences, cultural environment and emotional memories.

It should be deeply rooted—so deeply that it can feel almost engraved into the body, creating the illusion that it has somehow been written into one’s DNA.

But my husband’s answer was direct and firm.

“No,” he said. “There is no age at which a language simply becomes fixed forever. Language is a form of muscle memory. If you do not use it, it declines. That does not happen only to children. It happens to adults as well.”

“I am forty-three now,” he continued. “If I stopped using one of my languages for a long time, it would definitely begin to deteriorate.”

His words stayed with me for a long time.

I grew up with only one mother tongue. I have never stood in the position of someone who once possessed two equally stable languages and then experienced one of them gradually withdrawing.

My instinct has therefore always told me that once a mother tongue has survived into adulthood, it should be stable. It should remain buried deeply inside the body.

Even though I now live abroad and Chinese is not the dominant language in my external environment, I still find it difficult to imagine that a language which has grown so deeply into a person could deteriorate simply because it is no longer being used.

Yet when I thought about it carefully, I realised that I could not entirely disagree with him.

The more I looked back at my own experience, the more I understood that my difficulty with German was not caused by a weak beginning. On the contrary, my foundation was quite solid, and I learned quickly.

After arriving in Germany, I attended a language course for three months and then completed a one-year university preparatory programme. I entered university with an average grade of 1.7—a strong result in the German grading system, in which 1.0 is the highest—and began writing academic work directly in German at a relatively early stage.

Strictly speaking, I was never someone who simply “could not learn the language.” During those first few years, I may even have progressed faster than many other people.

So when I later failed to develop a strong sense of having an inner life in German, I gradually began to feel that the reason was not necessarily the language itself. It may have had more to do with the way I chose to live.

Perhaps I was simply never the kind of person who wanted to immerse herself, little by little, in German society.

In fact, the period in which I had the closest and most frequent contact with Germans was probably during my student years. At the time, I worked as a background performer at an American military base for around ninety days each year.

Almost all my colleagues were German, and during those periods we worked, ate and lived together virtually around the clock. That was probably the closest I ever came to living alongside Germans continuously and at close range.

Yet even in that environment, I did not naturally become someone who felt deeply “integrated.”

It was not because I was unable to communicate or because I had nothing to say. Quite the opposite: when I met someone with whom I shared an interest, I could have very deep conversations. I could also speak for a long time with someone I had never met before, even in an unfamiliar setting.

My problem was never that I could not open my mouth, nor that my German was insufficient for conversation.

Looking back now, I feel that this may not have been merely a question of opportunity. It may have been more a question of personality.

It was not that no door had been open to me. I simply never truly walked through it.

The deeper issue may be that I have always maintained a very strong sense of personal boundaries. I have my own way of living, my own rhythm and my own set of habits.

I am not someone who is particularly willing to reshape her entire self gradually in order to fit into a particular environment.

Families who integrate very successfully often begin to spend time naturally with German friends. They meet for meals, attend local activities together, and gradually allow their home life, social habits and language practices to move closer to German society.

In some families, even their food, friendship networks and the cultural centre of their daily interactions gradually shift almost entirely towards Germany.

That is not my personality.

Regardless of whom I live with, I stubbornly preserve a part of myself. There are many fundamental habits in my life that I am reluctant to change, and I have never been eager to place myself voluntarily in a state of deep assimilation.

Looking back, I therefore feel that my limited sense of integration over the years may not simply have been a language issue. It may have reflected a deeper choice about how I wanted to live.

It was not that I was incapable of living differently. I simply never truly wanted to turn myself into that kind of person.

A few days ago, I happened to read an article published on a WeChat gōngzhònghào². The author wrote that after arriving in Germany, she worked extremely hard on her German, progressing from zero to C1 within a year. She also made a sustained effort to integrate into German society.

Even so, she eventually realised that a subtle distance remained between her and her German colleagues.

During a single conversation or spontaneous exchange, those colleagues might absorb a kind of understanding that she herself would need several days of market research and reading to construct.

I strongly identified with what she wrote.

It reminded me that linguistic proficiency and a genuine sense of belonging are not the same thing.

Being able to speak, write and handle practical matters—even being able to complete one’s education and perform one’s job—does not necessarily mean that one has truly entered the social instincts, networks of relationships and unspoken cultural understandings that exist behind a language.

This is why I increasingly believe that what determines whether a language survives and continues to grow is not merely the point at which it began, nor the grades someone achieved in an examination.

What matters is the position that language later occupies within a person’s life.

Is it the language of your relationships?

Is it the language of your work?

Is it the language you naturally use when forming friendships?

Is it the language you instinctively switch into when thinking about complicated questions, expressing subtle emotions or interpreting cultural hints?

When it is none of these things, even a language that someone spoke fluently during childhood can gradually become a language they “know” but no longer truly live within.

Seen from this perspective, I increasingly feel that many people are eventually left with only one “real mother tongue” not because the other language was weak from the beginning, nor because they failed to acquire it during childhood.

It happens because language is never something that is learned once and then preserved forever in exactly the same condition.

It is more like a living ability—a state that must continually be used, activated and maintained.

When you use a language, it remains alive.

When you leave it unused for a long time, it gradually becomes blunt and begins to withdraw.

In an unexpected way, this may actually have benefited my daughter’s Chinese.

Unlike some families who have become deeply integrated into German society, I have not allowed the centre of our family life to shift almost entirely towards German and German-speaking social circles.

Inside our home, another language and another cultural position have always remained stable, clearly defined and present.

Because of this, the decline, stagnation or rapid deterioration of Chinese that often begins in other families once children enter primary or secondary school has not been nearly as noticeable in my daughter.

Looking back now, I think this may be connected to my own experiences and personality—and perhaps even to a certain unwillingness on my part to be carried away completely by the surrounding environment.

Only after writing all of this did I realise that the question I had been trying to discuss might need to be asked differently.

Perhaps we should not ask only whether a child can possess two mother tongues.

Perhaps the more important question is whether both of those languages will still occupy a real place in that child’s life ten or twenty years later.

Because the fate of a language is never determined solely by how it was first acquired.

It is determined by whether it continues to be used.

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Notes

1. Bǎomā (宝妈): Literally formed from bǎobǎo, meaning “baby” or “precious child,” and mā, meaning “mother,” bǎomā is a widely used term in contemporary Chinese online culture. It generally refers to mothers of young children, especially women who participate in parenting communities, discuss childcare and family education online, or organise a significant part of their identity and daily life around raising children. Although it can simply mean “mother,” its tone and social associations are not fully captured by the neutral English word.

2. Gōngzhònghào (公众号): Usually translated as a “WeChat Official Account,” this is a publishing and subscription channel within WeChat, China’s dominant multipurpose communication platform. Individuals, writers, media organisations and businesses use these accounts to publish long-form articles and distribute them directly to subscribers. A gōngzhònghào shares certain features with a newsletter, blog or platform such as Medium, but it is much more deeply embedded in Chinese social networks and everyday digital life.

This essay is also available in other languages:

Chinese version: 为什么很多孩子明明长出了两套母语系统，后来却只剩下一种？

German version: Warum entwickeln viele Kinder zwei muttersprachliche Systeme – und behalten später doch nur eines?