How Do Children Acquire Grammar?
From Examples to Phrases, Constructions, and Syntax

Early grammar development begins with concrete expressions that appear again and again in everyday life. Examples include sentences such as I want milk. I want juice. I want this. I want mommy.

After hearing sentences like these many times, children notice that the part I want repeats, while different words follow it. What first seemed like separate sentences begins to reveal a shared pattern: I want ___. For children, the earliest form of grammar is not an explanation of what an object is; instead, they begin to understand sentences through a slot-and-frame pattern, where a fixed frame stays in place and words can be swapped into the open slot.

Grammar does not appear only in word order. In English, much grammatical information is carried in actual speech by short function words and word endings. Children are not analyzing sentences from the start as “be + present participle = progressive.” But by hearing large numbers of sentences, they experience the fact that certain forms are likely to appear after certain function words.

Even without being explicitly taught grammar, children can gradually discover sentence structure by learning where function words and morphemes appear, and what kinds of words tend to come before and after them.

The same is true of small morphemes attached to words. Children repeatedly hear expressions such as one dog / two dogs; a book / three books. As a result, they experience that in situations involving more than one item, the noun is likely to end in -s.

Likewise, when children are exposed to many examples such as I like dogs. You like dogs. He likes dogs., they also learn that the verb is likely to take -s when the subject is he or she. Even though both endings are pronounced /s/, they occur after different kinds of words and in different contexts, so through repeated experience, children begin to separate their different functions.

Function words themselves also have strong distributional patterns. If children keep hearing a dog, a car, a book, they begin to notice that a certain kind of noun is likely to follow a. If they experience many examples like to eat, to play, to go, they begin to see the pattern that a verb tends to come after to.

As these predictions accumulate, children develop patterns of sentence structure such as “this kind of word comes in this position” or “when this small word appears, this kind of unit tends to follow,” even without knowing grammatical terminology.

Alongside patterns involving function words and morphemes, children also learn larger sentence patterns. Imagine they encounter many expressions such as Give me the book. Give me your hand. Show me the picture. Tell me a story. The verbs and nouns differ, but the same underlying relationship is present: someone gives, shows, or tells something to someone else.

What begins as the concrete chunk Give me... gradually expands, through repeated exposure, into a more abstract pattern that can be used with other verbs as well. In this sense, finding a common pattern across specific examples and extending it to new expressions can be understood as constructional generalization.

Patterns of different sizes—function words, morphemes, fixed expressions, phrases, and whole sentences—overlap and work together to build a grammatical system.

When we hear How are you?, we do not usually analyze it word by word as How = question word, are = verb, and you = subject. Because we have heard and used it many times, we can process it as a single unit.

Words that frequently appear together are easier to remember as a chunk. As the number of these fixed expressions grows, there is less need to process one word at a time, and language processing becomes faster. In addition, when children experience multiple similar fixed expressions, the shared elements across them begin to reveal more abstract grammar. Frequency provides the raw material for discovering grammatical patterns and processing them automatically.

When people think of grammar, they often imagine rules for word order or inflection. But the constructions children acquire also carry meaning. For example, in John broke the window., John performs some action that causes a change in the window. In contrast, The window broke. focuses not on who broke it, but on the change that happened to the window itself.

As children experience many real examples, they learn at the same time that “this form expresses this kind of meaning”—that is, they acquire a mapping between form and meaning. Grammar is not completed by the distribution of function words and morphemes alone. Word order and the meanings of constructions are added as well, and together they build the overall structure of the sentence.

Children’s grammar is not fully formed from the start in the same way as an adult’s. Early on, many expressions are tied to specific words, and as experience grows, the range of usable patterns gradually expands. For example, what first exists as the chunk I want... later expands to other expressions such as I need..., I like..., I see....

As patterns of different sizes connect with one another, children begin to see a sentence system that goes beyond individual expressions. Development moves from fixed expressions to phrases, from the distribution of function words and morphemes to sentence structure, and from constructions to more abstract syntax.

Being able to explain that “you add -s in the third-person singular” is not the same as being able to say He likes soccer. in conversation without thinking. Likewise, knowing that “the present progressive is be + present participle” is not the same as instantly grasping the meaning of She is playing outside. the moment you hear it.

The latter requires extensive experience with real examples and repeated processing of the same function words, morphemes, and sentence patterns. Native speakers acquire, from large numbers of examples, the distributions that tell them what kinds of forms appear after be, what comes after can, and what small endings attach to nouns and verbs—and they process these patterns automatically.

Even in second-language learning, automatic grammatical understanding grows not only from being told about grammar, but from hearing and reading large numbers of real sentences and experiencing how function words, morphemes, word order, and constructions actually appear.